The Project Gutenberg EBook of Scientific American Supplement, No. 467,
December 13, 1884, by Various

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Title: Scientific American Supplement, No. 467, December 13, 1884

Author: Various

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  Scientific American Supplement, Vol. XVIII No. 467. }
  Scientific American, established 1845. }


  NEW YORK, DECEMBER 13, 1884.

  { Scientific American Supplement, $5 a year.
  { Scientific American and Supplement, $7 a year.




THE NEW BUILDING OF THE TECHNICAL HIGH SCHOOL OF BERLIN.


The Berlin Academy of Industry and the Academy of Building were united
in 1876 to form the Technical High School. It was found that the
buildings were not sufficiently large for the great number of scholars,
and arrangements were made for erecting new buildings affording
better accommodations. The first design was made by Lucal, who, after
his death, was succeeded by Hitzig, who died in 1821, and who was
succeeded, in turn, by Mr. Raschdorff.

The main building is shown in the annexed cut, taken from the
_Illustrirte Zeitung_. It is four stories high and 754 ft. long,
and the middle and side wings are about 656 ft. deep, the portions
between the wings being about 164 ft. deep. In the interior five
square courts are arranged, of which two are at the right and two at
the left, and are separated by intermediate building. The middle court
in the central portion of the building is covered by a glass roof and
forms a vestibule surrounded by arcades, the halls of which lead to
different rooms. In the middle portion are the rooms for the officers,
and the reading rooms. The courts are erected in brick with sgraffito
ornamentation; and the front, sides, and rear are erected in sandstone
on a granite base. The first story, or ground floor, is of a yellowish
color, and the upper story is of a clear whitish-gray. The building is
richly ornamented by statues, busts, reliefs, and groups representing
the different architects, artists, scientists, etc.

[Illustration: THE NEW TECHNICAL HIGH SCHOOL AT BERLIN.]




THE NEW UNIVERSITY BUILDINGS AT STRASSBURG.


The buildings of the University of Strassburg are arranged in two
groups; one in the northern and the other in the southern part of the
city. All the buildings of the medical department were erected in the
neighborhood of the hospital, which is located between the south wall
of the city and the River Ill.

In front of the old "Fischerthor," or Fishergate, the college house,
or college building proper, in which are located the offices, lecture
rooms, etc., was erected. A front perspective view of this building is
shown in the lower part of the annexed cut, taken from the _Illustrirte
Zeitung_. Behind this main building, and between the Universitaets and
Goethe Strasse, the buildings of the Chemical Institute, the Physical
Institute, with its tower; the Botanical Institute, with the gardens
and hothouses, and the Astronomical Institute, with its observatory
and movable dome, are located. These buildings were designed by the
architects Hermann, Eggert, Brion, and Salomon, all of Strassburg.

[Illustration: GENERAL VIEW OF THE STRASSBURG UNIVERSITY BUILDINGS.]

[Illustration: THE COLLEGE HOUSE OF THE STRASSBURG UNIVERSITY.]

The main building was designed by Prof. Warth, of Karlsruhe, and the
style of the same is a noble Italian renaisance of the early period.
Upon a base of red sandstone the basement is erected in freestone
rustic masonry, upon which the first story is erected in smooth stone
with conspicuous joints. The top story is constructed with arched
windows separated by Ionic columns or pilasters. The central portion,
which projects from the front of the building, has a grand staircase
and two corner pavilions. The upper part of the central portion is
constructed with fluted Corinthian columns, between which niches are
provided, in which busts of the ideal representatives of the faculties
are placed, viz., Homer, Paulus, Solon, Hippocrates, Aristotle, and
Archimedes. Above the cornice, in the tympanum, is placed a group, of
which Athene, with the torch of science, is the main figure. In the
niches in the pavilions at the corners of the middle portion are the
statues of Germania and Argentina, the representative of the free city
of Strassburg. The pavilions at the ends of the building are ornamented
by thirty-six statues of German scientists. The middle portion of the
building directly beyond the grand staircase is occupied by a large
open court, having a rich glass roof. The left part of the lower story
is divided into lecture rooms, and the right side into rooms for the
officers, etc. The collections are in the upper story, and the chapel,
or main hall, is in the middle of the building.




THE WAVE THEORY OF LIGHT.[1]

By Sir WILLIAM THOMSON, F.R.S., LL.D., etc.


[1] A Lecture delivered at the Academy of Music, Philadelphia, under
the auspices of the Franklin Institute, September 29, 1884.

The subject upon which I am to speak to you this evening is happily for
me not new in Philadelphia. The beautiful lectures on light which were
given several years ago by President Morton, of the Stevens Institute,
and the succession of lectures on the same subject so admirably
illustrated by Prof. Tyndall, which many now present have heard, have
fully prepared you for anything I can tell you this evening in respect
to the wave theory of light.

It is indeed my humble part to bring before you some mathematical and
dynamical details of this great theory. I cannot have the pleasure
of illustrating them to you by anything comparable with the splendid
and instructive experiments which many of you have already seen. It
is satisfactory to me to know that so many of you now present are so
thoroughly prepared to understand anything I can say, that those who
have seen the experiments will not feel their absence at this time. At
the same time I wish to make them intelligible to those who have not
had the advantages to be gained by a systematic course of lectures. I
must say in the first place, without further preface, as time is short
and the subject is long, simply that sound and light are both due to
vibrations propagated in the manner of waves; and I shall endeavor in
the first place to define the manner of propagation and mode of motion
that constitute those two subjects of our senses, the sense of sound
and the sense of light.

Each is due to vibrations. The vibrations of light differ widely
from the vibrations of sound. Something that I can tell you more
easily than anything in the way of dynamics or mathematics respecting
the two classes of vibrations is, that there is a great difference
in the frequency of the vibrations of light when compared with the
frequency of the vibrations of sound. The term "frequency," applied to
vibrations, is a convenient term, applied by Lord Rayleigh in his book
on sound to a definite number of full vibrations of a vibrating body
per unit of time. Consider, then, in respect to sound, the frequency
of the vibrations of notes, which you all know in music represented
by letters, and by the syllables for singing the do, re, mi, etc.
The notes of the modern scale correspond to different frequencies of
vibrations. A certain note and the octave above it correspond to a
certain number of vibrations per second and double that number.

I may explain in the first place conveniently the note called "C;"
I mean the middle "C." I believe it is the C of the tenor voice,
that most nearly approaches the tones used in speaking. That note
corresponds to two hundred and fifty-six full vibrations per second,
two hundred and fifty-six times to and fro per second of time.

Think of one vibration per second of time. The seconds pendulum of the
clock performs one vibration in two seconds, or a half vibration in one
direction per second. Take a 10-inch pendulum of a drawing-room clock,
which vibrates twice as fast as the pendulum of an ordinary eight-day
clock, and it gives a vibration of one per second, a full period of one
per second to and fro. Now think of three vibrations per second. I can
move my hand three times per second easily, and by a violent effort I
can move it to and fro five times per second. With four times as great
force, if I could apply it, I could move it twice five times per second.

Let us think, then, of an exceedingly muscular arm that would cause it
to vibrate ten times per second, that is, ten times to the left and ten
times to the right. Think of twice ten times, that is, twenty times per
second, which would require four times as much force; three times ten,
or thirty times a second, which require nine times as much force. If a
person were nine times as strong as the most muscular arm can be, he
could vibrate his hand to and fro thirty times per second, and without
any other musical instrument could make a musical note by the movement
of his hand which would correspond to one of the pedal notes of an
organ.

If you want to know the length of a pedal pipe, you can calculate it in
this way. There are some numbers you must remember, and one of them is
this. You, in this country, are subjected to the British insularity in
weights and measures; you use the foot and inch and yard. I am obliged
to use that system, but I apologize to you for doing so, because it
is so inconvenient, and I hope all Americans will do everything in
their power to introduce the French metrical system. I hope the evil
action performed by an English minister whose name I need not mention,
because I do not wish to throw obloquy on any one, may be remedied. He
abrogated a useful rule, which for a short time was followed and which
I hope will soon be again enjoined, that the French metrical system
be taught in all our national schools. I do not know how it is in
America. The school system seems to be very admirable, and I hope the
teaching of the metrical system will not be let slip in the American
schools any more than the use of the globes.

I say this seriously. I do not think any one knows how seriously
I speak of it. I look upon our English system as a wickedly
brain-destroying piece of bondage under which we suffer. The reason
why we continue to use it is the imaginary difficulty of making a
change, and nothing else; but I do not think that in America any such
difficulty should stand in the way of adopting so splendidly useful a
reform.

I know the velocity of sound in feet per second. If I remember rightly,
it is 1,089 feet per second in dry air at the freezing point, and 1,115
feet per second in air of what we call moderate temperature, 59 or 60
degrees (I do not know whether that temperature is ever attained in
Philadelphia or not; I have had no experience of it, but people tell
me it is sometimes 59 or 60 degrees in Philadelphia, and I believe
them); in round numbers let us call it 1,000 feet per second. Sometimes
we call it a thousand musical feet per second, it saves trouble in
calculating the length of organ pipes; the time of vibration in an
organ pipe is the time it takes a vibration to run from one end to the
other and back. In an organ pipe 500 feet long the period would be one
per second; in an organ pipe 10 feet long the period would be 50 per
second; in an organ pipe 20 feet long the period would be 25 per second
at the same rate. Thus 25 per second and 50 per second of frequencies
correspond to the periods of organ pipes of 20 feet and 10 feet.

The period of vibration of an organ pipe, open at both ends, is
approximately the time it takes sound to travel from one end to the
other and back. You remember that the velocity in dry air in a pipe
10 feet long is a little more than 50 periods per second; going up to
256 periods per second, the vibrations correspond to those of a pipe 2
feet long. Let us take 512 periods per second; that corresponds to a
pipe about a foot long. In a flute, open at both ends, the holes are so
arranged that the length of the sound wave is about 1 foot, for one of
the chief "open notes." Higher musical notes correspond to greater and
greater frequency of vibration, viz., 1,000, 2,000, 4,000 vibrations
per second; 4,000 vibrations per second correspond to a piccolo flute
of exceedingly small length; it would be but one and a half inches
long. Think of a note from a little dog call, or other whistle one and
a half inches long, open at both ends, or from a little key having a
tube three-quarters of an inch long, closed at one end; you will then
have 4,000 vibrations per second.

A wave length of sound is the distance traversed in the period of
vibration. I will illustrate what the vibrations of sound are by this
condensation traveling along our picture on the screen. Alternate
condensations and rarefactions of the air are made continuously by a
sounding body. When I pass my hand vigorously in one direction, the
air before it becomes dense, and the air on the other side becomes
rarefied. When I move it in the other direction, these things become
reversed; there is a spreading out of condensation from the place
where my hand moves in one direction and then in the reverse. Each
condensation is succeeded by a rarefaction. Rarefaction succeeds
condensation at an interval of one-half what we call "wave lengths."
Condensation succeeds condensation at the full interval of what we call
wave lengths.

We have here these luminous particles on this scale,[2] representing
portions of the air close together, dense; a little higher up, portions
of air less dense. I now slowly turn the handle of the apparatus in
the lantern, and you see the luminous sectors showing condensation
traveling slowly upward on the screen; now you have another
condensation; making one wave length.

[2] Alluding to a moving diagram of wave motion of sound produced by a
working slide for lantern projection.

This picture or chart represents a wave length of four feet. It
represents a wave of sound four feet long. The fourth part of a
thousand is 250. What we see now of the actual scale represents the
lower note C of the tenor voice. The air from the mouth of a singer is
alternately condensed and rarefied just as you see here.

But that process shoots forward at the rate of one thousand feet per
second; the exact period of the motion is 256 vibrations per second for
the actual case before you. Follow one particle of the air forming part
of a sound wave, as represented by these moving spots of light on the
screen; now it goes down, then another portion goes down rapidly; now
it stops going down; now it begins to go up; now it goes down and up
again.

As the maximum of condensation is approached, it is going up with
diminishing maximum velocity. The maximum of rarefaction has now
reached it, and the particle stops going up and begins to move down.
When it is of mean density the particles are moving with maximum
velocity, one way or the other. You can easily follow these motions,
and you will see that each particle moves to and fro, and the thing
that we call _condensation_ travels along.

I shall show the distinction between these vibrations and the
vibrations of light. Here is the fixed appearance of the particles when
displaced but not in motion. You can imagine particles of something,
the thing whose motion constitutes light. This thing we call the
luminiferous ether. That is the only substance we are confident of
in dynamics. One thing we are sure of, and that is the reality and
substantiality of the luminiferous ether. This instrument is merely
a method of giving motion to a diagram designed for the purpose of
illustrating wave motion of light. I will show you the same thing in a
fixed diagram, but this arrangement shows the mode of motion.

Now follow the motion of each particle. This represents a particle of
the luminiferous ether, moving at the greatest speed when it is at the
middle position.

You see two modes of vibration,[3] sound and light now moving
together--the traveling of the wave of condensation and rarefaction,
and the traveling of the wave of transverse displacement. Note the
direction of propagation. Here it is from your left to your right, as
you look at it. Look at the motion when made faster. We have now the
direction reversed. The propagation of the wave is from right to left,
again the propagation of the wave is from left to right; each particle
moves perpendicularly to the line of propagation.

[3] Showing two moving diagrams, simultaneously, on the screen,
depicting a wave motion of light, the other a sound vibration.

I have given you an illustration of the vibration of sound waves,
but I must tell you that the movement illustrating the condensation
and rarefaction represented in that moving diagram are necessarily
very much exaggerated to let the motion be perceptible, whereas the
greatest condensation in actual sound motion is not more than one or
two per cent, or a small fraction of a per cent. Except that the amount
of condensation was exaggerated in the diagram for sound, you have a
correct representation of what actually takes in the low note C.

On the other hand, in the moving diagram representing light waves what
had we? We had a great exaggeration of the inclination of the line of
particles. You must first imagine a line of particles in a straight
line, and then you must imagine them disturbed into a wave curve, the
shape of the curve corresponding to the disturbance. Having seen what
the propagation of the wave is, look at this diagram and then look at
that one. This, in light, corresponds to the different sounds I spoke
of at first. The wave length of light is the distance from crest to
crest of the wave, or from hollow to hollow. I speak of crests and
hollows, because we have a diagram of ups and downs as the diagram is
placed.

[Illustration: Waves of Red Light.]

[Illustration: Waves of Violet Light.]

Here, then, you have a wave length.[4] In this lower diagram you have
the wave length of violet light. It is but one-half the length of
the upper wave of red light; the period of vibration is but half as
long. Now, on an enormous scale, exaggerated not only as to slope, but
immensely magnified as to wave length, we have an illustration of the
waves of light. The drawing marked "red" corresponds to red light, and
this lower diagram corresponds to violet light. The upper curve really
corresponds to something a little below the red ray of light in the
spectrum, and the lower curve to something beyond the violet light. The
variation in length between the most extreme rays is in the proportion
of four and a half of red to eight of the violet, instead of four and
eight; the red waves are nearly as one to two of the violet.

[4] Exhibiting a large drawing, or chart, representing a red and a
violet wave of light.

To make a comparison between the number of vibrations for each wave
of sound and the number of vibrations constituting light waves, I may
say that 30 vibrations per second is about the smallest number which
will produce a musical sound; 50 per second give one of the grave pedal
notes of an organ, 100 or 200 per second give the low notes of the bass
voice, higher notes with 250 per second, 300 per second, 1,000, 4,000,
up to 8,000 per second, give about the shrillest notes audible to the
human ear.

Instead of the numbers, which we have, say, in the most commonly used
part of the musical scale, _i. e._, from 200 or 300 to 600 or 700 per
second, we have millions and millions of vibrations per second in light
waves; that is to say, 400 million million per second, instead of 400
per second. That number of vibrations is performed when we have red
light produced.

An exhibition of red light traveling through space from the remotest
star is due to the propagation by waves or vibrations, in which each
individual particle of the transmitting medium vibrates to and fro 400
million million times in a second.

Some people say they cannot understand a million million. Those people
cannot understand that twice two makes four. That is the way I put it
to people who talk to me about the incomprehensibility of such large
numbers. I say _finitude_ is incomprehensible, the infinite in the
universe _is_ comprehensible. Now apply a little logic to this. Is the
negation of infinitude incomprehensible? What would you think of a
universe in which you could travel one, ten, or a thousand miles, or
even to California, and then find it come to an end? Can you suppose an
end of matter, or an end of space? The idea is incomprehensible. Even
if you were to go millions and millions of miles, the idea of coming to
an end is incomprehensible.

You can understand one thousand per second as easily as you can
understand one per second. You can go from one to ten, and ten times
ten and then to a thousand without taxing your understanding, and then
you can go on to a thousand million and a million million. You can all
understand it.

Now 400 million million vibrations per second is the kind of thing
that exists as a factor in the illumination by red light. Violet
light, after what we have seen and have illustrated by that curve, I
need not tell you corresponds to vibrations of 800 million million per
second. There are recognizable qualities of light caused by vibrations
of much greater frequency and much less frequency than this. You may
imagine vibrations having about twice the frequency of violet light and
one fifteenth the frequency of red light, and still you do not pass
the limit of the range of continuous phenomena only a part of which
constitutes _visible_ light.

Everybody knows the "photographer's light," and has heard of
_invisible_ light producing visible effects upon the chemically
prepared plate in the camera. Speaking in round numbers, I may say
that, in going up to about twice the frequency I have mentioned for
violet light, you have gone to the extreme end of the range of known
light of the highest rates of vibration; I mean to say that you have
reached the greatest frequency that has yet been observed.

When you go below visible red light, what have you? We have something
we do not see with the eye, something that the ordinary photographer
does not bring out on his photographically sensitive plates. It is
light, but we do not see it. It is something so closely continuous with
light visible, that we may define it by the name of invisible light.
It is commonly called radiant heat; invisible radiant heat. Perhaps,
in this thorny path of logic, with hard words flying in our faces, the
least troublesome way of speaking of it is to call it radiant heat. The
heat effect you experience when you go near a bright, hot coal fire,
or a hot steam boiler; or when you go near, but not over, a set of hot
water pipes used for heating a house; the thing we perceive in our face
and hands when we go near a boiling pot and hold the hand on a level
with it, is radiant heat; the heat of the hands and face caused by a
hot fire, or a hot kettle when held under the kettle, is also radiant
heat.

You might readily make the experiment with an earthen teapot; it
radiates heat better than polished silver. Hold your hands below,
and you perceive a sense of heat; above the teapot you get more
heat; either way you perceive heat. If held over the teapot, you
readily understand that there is a little current of air rising. If
you put your hand under the teapot, you get cold air; the upper side
of your hand is heated by radiation, while the lower side is fanned
and is actually cooled by virtue of the heated kettle above it.

That perception by the sense of heat is the perception of something
actually continuous with light. We have knowledge of rays of radiant
heat perceptible down to (in round numbers) about four times the wave
length, or one-fourth the period of visible or red light. Let us take
red light at 400 million million vibrations per second; then the lowest
radiant heat, as yet investigated, is about 100 million million per
second in the way of frequency of vibration.

I had hoped to be able to give you a lower figure. Prof. Langley
has made splendid experiments on the top of Mount Whitney, at the
height of 1,500 feet above the sea level, with his "bolometer," and
has made actual measurements of the wave lengths of radiant heat
down to exceedingly low figures. I will read you one of the figures;
I have not got it by heart yet, because I am expecting more from
him.[5] I learned a year and a half ago that the lowest radiant heat
observed by the diffraction method of Prof. Langley corresponded to 28
one-hundred-thousandths of a centimeter for wave length, 28 as compared
with red light, which is 7.3, or nearly fourfold. Thus wave lengths of
four times the amplitude or one-fourth the frequency per second of red
light have been experimented on by Prof. Langley, and recognized as
radiant heat.

[5] Since my lecture I have heard from Prof. Langley that he has
measured the refrangibility by a rock salt prism, and inferred the wave
length of heat rays from a "Leslie cube" (a metal vessel of hot water
radiating from a blackened side). The greatest wave length he has thus
found is one one-thousandth of a centimeter, which is seventeen times
that of sodium light. The corresponding period is about thirty million
million to the second.--W.T.

Photographic or actinic light, as far as our knowledge extends at
present, takes us to a little less than one-half the wave length of
violet light. You will thus see that while our acquaintance with wave
motion below the red extends down to one-quarter of the slowest rate
which affects the eye, our knowledge of vibrations at the other end of
the scale only comprehends those having twice the frequency of violet
light. In round numbers, we have four octaves of light, corresponding
to four octaves of sound in music. In music the octave has a range to a
note of double frequency. In light we have one octave of visible light,
one octave above the visible range, and two octaves below the visible
range. We have one hundred per second, two hundred per second, four
hundred per second (million million understood) for invisible radiant
heat, eight hundred per second for visible light, and one thousand six
hundred per second for invisible light.

One thing in common to the whole is the heat effect. It is extremely
small in moonlight, so small that nobody until recently knew there was
any heat in the moon's rays. Herschel thought it was perceptible in
our atmosphere by noticing that it dissolved away very light clouds,
an effect which seemed to show in full moonlight more than when we
have less than full moon. Herschel, however, pointed this out as
doubtful, but now, instead of its being a doubtful question, we have
Prof. Langley giving as a fact that the light from the moon drives the
indicator of his sensitive instrument clear across the scale, and with
a comparatively prodigious heating effect!

I must tell you that if any of you want to experiment with the heat of
the moonlight, you must compare the heat with whatever comes within the
influence of the moon's rays only. This is a very necessary precaution;
if, for instance, you should take your bolometer or other heat detecter
from a comparatively warm room into the night air, you would obtain an
indication of a fall in temperature owing to this change. You must be
sure that your apparatus is in thermal equilibrium with the surrounding
air, then take your burning glass, and first point it to the moon and
then to space in the sky beside the moon; you thus get a differential
measurement in which you compare the radiation of the moon with the
radiation of the sky. You will then see that the moon has a distinctly
heating effect.

To continue our study of visible light, that is, undulations extending
from red to violet in the spectrum (which I am going to show you
presently), I would first point out on this chart that in the section
from letter A to letter D, we have visual effect and heating effect
only; but no ordinary chemical or photographic effect.

[Illustration: The Solar Spectrum.]

Photographers can leave their usual sensitive, chemically prepared
plates exposed to yellow light and red light without experiencing any
sensible effect; but when you get toward the blue end of the spectrum,
the photographic effect begins to tell, more and more as you get toward
the violet end. When you get beyond the violet, there is the invisible
light known chiefly by its chemical action. From yellow to violet we
have visual effect, heating effect, and chemical effect, all three;
above the violet, only chemical and heating effect, and so little of
the heating effect that it is scarcely perceptible.

The prismatic spectrum is Newton's discovery of the composition of
white light. White light consists of every variety of color from red
to violet. Here, now, we have Newton's prismatic spectrum produced by
a prism. I will illustrate a little in regard to the nature of color
by putting something before the light which is like colored glass;
it is colored gelatin. I will put in a plate of red gelatin which is
carefully prepared of chemical materials, and see what that will do. Of
all the light passing to it from violet to red, it only lets through
the red and orange, giving a mixed reddish color.

Here is another plate of green gelatin. The green absorbs all the red,
giving only green. Here is another plate absorbing something from each
portion of the spectrum, taking away a great deal of the violet and
giving a yellow or orange appearance to the light. Here is another
absorbing out the green, leaving red, orange, and a very little faint
green, and absorbing out all the violet.

When the spectrum is very carefully produced, far more perfectly than
Newton knew how to show it, we have a homogeneous spectrum. It must
be noticed that Newton did not understand what we call a homogeneous
spectrum; he did not produce it, and does not point out in his writings
the conditions for producing it. With an exceedingly fine line of light
we can bring it out as in sunlight, like this upper picture, red,
orange, yellow, green, blue, indigo, and violet according to Newton's
nomenclature. Newton never used a narrow beam of light, and so could
not have had a homogeneous spectrum.

This is a diagram painted on glass and showing the colors as we know
them. It would take two or three hours if I were to explain the
subject of spectrum analysis to-night. We must tear ourselves away
from it. I will just read out to you the wave lengths corresponding
to the different positions in the sun's spectrum of certain dark
lines commonly called "Fraunhofer's lines." I will take as a unit the
one-hundred-thousandth of a centimeter. A centimeter is 0.4 of an
inch; it is a rather small half an inch. I take the thousandth of a
centimeter and the hundred of that as a unit. At the red end of the
spectrum the light in the neighborhood of that black line A has for its
wave length 7.6; B has 6.87; D has 5.89; the "frequency" for A is 3.9
times 100 million million; the frequency of D light is 5.1 times 100
million million per second.

Now, what force is concerned in those vibrations as compared with
sound at the rate of 400 vibrations per second? Suppose for a moment
the same matter was to move to and fro through the same range but
400 million million times per second. The force required is as the
square of the number expressing the frequency. Double frequency would
require quadruple force for the vibration of the same body. Suppose I
vibrate my hand again, as I did before. If I move it once per second, a
moderate force is required; for it to vibrate ten times per second, 100
times as much force is required; for 400 vibrations per second, 160,000
times as much force.

If I move my hand once per second through a space of a quarter of
an inch; a very small force is required; it would require very
considerable force to move it ten times a second, even through so small
a range; but think of the force required to move a tuning fork 400
times a second; compare that with the force required for a motion of
400 million million times a second. If the mass moved is the same, and
the range of motion is the same, then the force would be one million
million million million times as great as the force required to move
the prongs of the tuning fork. It is as easy to understand that number
as any number like 2, 3, or 4.

Consider gravely what that number means, and what we are to infer from
it. What force is there in space between my eye and that light? What
forces are there in space between our eyes and the sun and our eyes and
the remotest visible star! There is matter and there is motion, but
what magnitude of force may there be?

I move through this "luminiferous ether" as if it were nothing. But
were there vibrations with such frequency in a medium of steel or
brass, they would be measured by millions and millions and millions of
tons action on a square inch of matter. There are no such forces in our
air. Comets make a disturbance in the air, and perhaps the luminiferous
ether is split up by the motion of a comet through it. So when we
explain the nature of electricity, we explain it by a motion of the
luminiferous ether. We cannot say that it is electricity. What can this
luminiferous ether be? It is something that the planets move through
with the greatest ease. It permeates our air; it is nearly in the same
condition, so far as our means of judging are concerned, in our air and
in the interplanetary space. The air disturbs it but little; you may
reduce the air by air pumps to the hundred thousandth of its density,
and you make little effect in the transmission of light through it.
The luminiferous ether is an elastic solid. The nearest analogy I can
give you is this jelly which you see.[6] The nearest analogy to the
waves of light is the motion, which you can imagine, of this elastic
jelly, with a ball of wood floating in the middle of it. Look there,
when with my hand I vibrate the little red ball up and down, or when I
turn it quickly round the vertical diameter, alternately in opposite
directions; that is the nearest representation I can give you of the
vibrations of luminiferous ether.

[6] Exhibiting a large bowl of clear jelly with a small red wooden ball
embedded in the surface near the center.

Another illustration is Scottish shoemaker's wax or Burgundy pitch, but
I know Scottish shoemaker's wax better. It is heavier than water, and
absolutely answers my purpose. I take a large slab of the wax, place it
in a glass jar filled with water, place a number of corks on the lower
side and bullets on the upper side. It is brittle like the Trinidad or
Burgundy pitch which I have in my hand. You can see how hard it is, but
if left to itself it flows like a fluid. The shoemaker's wax breaks
with a brittle fracture, but it is viscous, and gradually yields.

What we know of the luminiferous ether is that it has the rigidity of
a solid, and gradually yields. Whether or not it is brittle and cracks
we cannot yet tell, but I believe the discoveries in electricity, and
the motions of comets and the marvelous spurts of light from them,
tend to show cracks in the luminiferous ether--show a correspondence
between the electric flash and the aurora borealis and cracks in the
luminiferous ether. Do not take this as an assertion, it is hardly
more than a vague scientific dream; but you may regard the existence
of the luminiferous ether as a reality of science, that is, we have
an all-pervading medium, an elastic solid, with a great degree of
rigidity; its rigidity is so prodigious in proportion to its density
that the vibrations of light in it have the frequencies I have
mentioned, with the wave lengths I have mentioned.

The fundamental question as to whether or not luminiferous ether
has gravity has not been answered. We have no knowledge that the
luminiferous ether is attracted by gravity; it is sometimes called
imponderable because some people vainly imagine that it has no weight.
I call it matter with the same kind of rigidity that this elastic jelly
has.

Here are two tourmalines; if you look through them toward the light,
you see the white light all around, _i. e._, they are transparent. If
I turn round one of these tourmalines the light is extinguished, it is
absolutely black, as though the tourmalines were opaque. This is an
illustration of what is called polarization of light. I cannot speak
to you about qualities of light without speaking of the polarization
of light. I want to show you a most beautiful effect of polarizing
light, before illustrating a little further by means of this large
mechanical illustration which you have in the bowl of jelly. Now I put
in the lantern another instrument called a "Nicol prism." What you
saw first were two plates of the crystal tourmaline which came from
Brazil, I believe, having the property of letting light pass when both
plates are placed in one particular direction as regards their axes of
crystallization, and extinguishing it when it passes through the first
plate held in another direction. We have now an instrument which also
gives rays of polarized light. A Nico prism is a piece of Iceland spar,
cut in two and turned, one part relatively to the other, in a very
ingenious way, and put together again, and cemented into one by Canada
balsam. The Nicol prism takes advantage of the property which the spar
has of double refraction, and produces the phenomenon which I now show
you.

I turn one prism round in a certain direction and you get light,
a maximum of light. I turn it through a right angle and you get
blackness. I turn it one-quarter round again and get maximum light;
one-quarter more, maximum blackness; one-quarter more, and bright
light. We rarely have such a grand specimen of a Nicol prism as this.

There is another way of producing polarized light. I stand before that
light, and look at its reflection in a plate of glass on the table
through one of the Nicol prisms, which I turn round, so. Now I must
incline that piece of glass at a particular angle, rather more than
forty-five degrees; I find a particular angle in which, if I look at
it and then turn the prism round in the hand, the effect is absolutely
to extinguish the light in one position and to give it maximum
brightness in another position. I use the term "absolute" somewhat
rashly. It is only a reduction to a very small quantity of light, not
an absolute annulment as we have in the case of the two Nicol prisms
used conjointly. Those of you who have never heard of this before would
not know what I am talking about. As to the mechanics of the thing,
it could only be explained to you by a course of lectures on physical
optics. The thing is this: vibrations of light must be in a definite
direction relatively to the line in which the light travels.

Look at this diagram: the light goes from left to right; we have
vibrations perpendicular to the line of transmission. There is a
line up and down, which is the line of vibration. Imagine here a
source of light, violet light, and here in front of it is the line of
propagation. Sound vibrations are to and fro; this is transverse to the
line of propagation. Here is another, perpendicular to the diagram,
still following the law of transverse vibration; here is another
circular vibration. Imagine a long rope: you whirl one end of it, and
you send a screw-like motion running along; you can get the circular
motion in one direction or in the opposite.

Plane polarized light is light with the vibrations all in a single
plane, perpendicular to the plane through the ray, which is technically
called the "plane of polarization." Circular polarized light consists
of undulations of luminiferous ether having a circular motion.
Elliptically polarized light is something between the two, not in a
straight line, and not in a circular line; the course of vibration
is an ellipse. Polarized light is light that performs its motions
continually in one mode or direction. If in a straight line, it is
plane polarized; if in a circular direction, it is circularly polarized
light; when elliptical, it is elliptically polarized light.

With Iceland spar, one unpolarized ray of light divides on entering
it into two rays of polarized light, by reason of its power of double
refraction, and the vibrations are perpendicular to one another in the
two emerging rays. Light is always polarized when it is reflected from
a plate of unsilvered glass, or water, at a certain definite angle of
fifty-six degrees for glass, fifty-two degrees for water, the angle
being reckoned in each case from a perpendicular to the surface. The
angle for water is the angle whose tangent is 1.4. I wish you to look
at the polarization with your own eyes. Light from glass at fifty
six degrees and from water at fifty-two degrees goes away vibrating
perpendicularly to the plane of incidence and plane of reflection.

We can distinguish it without the aid of an instrument. There is a
phenomenon well known in physical optics as "Haidinger's brushes." The
discoverer is well known in Philadelphia as a mineralogist, and the
phenomenon I speak of goes by his name. Look at the sky in a direction
of ninety degrees from the sun, and you will see a yellow and blue
cross, with the yellow toward the sun, and from the sun, spreading
out like two foxes' tails with blue between, and then two red brushes
in the space at right angles to the blue. If you do not see it, it is
because your eyes are not sensitive enough, but a little training will
give them the needed sensitiveness.

If you cannot see it in this way, try another method. Look into a pail
of water with a black bottom; or take a clear glass dish of water, rest
it on a black cloth and look down at the surface of the water on a
day with a white cloudy sky (if there is such a thing ever to be seen
in Philadelphia). You will see the white sky reflected in the basin
of water at an angle of about fifty degrees. Look at it with the head
tipped to one side, and then again with the head tipped to the other
side, keeping your eyes on the water, and you will see Haidinger's
brushes. Do not do it fast, or you will make yourself giddy. The
explanation of this is the refreshing of the sensibility of the retina.
The Haidinger's brush is always there, but you do not see it because
your eye is not sensitive enough. After once seeing it, you always see
it; it does not thrust itself inconveniently before you when you do not
want to see it. You can readily see it in a piece of glass with dark
cloth below it, or in a basin of water.

I am going to conclude by telling you how we know the wave lengths
of light and how we know the frequency of the vibrations. We shall
actually make a measurement of the wave length of the yellow light. I
am going to show you the diffraction spectrum.

You see on the screen,[7] on each side of a central white bar of light,
a set of bars of light variegated colors, the first one, on each side,
showing blue or indigo color, about four inches from the central white
bar and red about four inches farther, with vivid green between the
blue and the red. That effect is produced by a grating with 400 lines
to the centimeter, engraved on glass, which I now hold in my hand.
The next grating has 3,000 lines on a Paris inch. You see the central
space, and on each side a large number of spectrums, blue at one end
and red at the other. The fact that, in the first spectrum, red is
about twice as far from the center as the blue, proves that a wave
length of red light is double that of blue light.

[7] Showing the chromatic bands thrown upon the screen from a
diffraction grating.

I will now show you the operation of measuring the length of a wave of
sodium light, that is, a light like that marked D on the spectrum, a
light produced by a spirit lamp with salt in it. The sodium vapor is
heated up to several thousand degrees, when it becomes self-luminous,
and gives such a light as we get by throwing salt upon a spirit lamp in
the game of snap dragon.

I hold in my hand a beautiful grating of glass silvered by Liebig's
process of metallic silver, a grating with 6,480 lines to the inch,
belonging to my friend Prof. Barker, which he has kindly brought here
for us this evening. You will see the brilliancy of color as I turn the
light reflected from the grating toward you and pass the beam around
the room. You have now seen directly with your own eyes these brilliant
colors reflected from the grating, and you have also seen them thrown
upon the screen from a grating placed in the lantern. With a grating
of 17,000 lines, a much greater number of lines per inch than the
other, you will see how much further from the central bright space the
first spectrum is; how much more this grating changes the direction or
diffraction of the beam of light. Here is the center of the grating,
and there is the first spectrum. You will note that the violet light
is least diffracted and the red light is most diffracted. This
diffraction of light first proved to us definitely the reality of the
undulatory theory of light.

You ask, Why does not light go round the corner as sound does? Light
goes round a corner in these diffraction spectrums; it is shown going
round a corner, it passes through these bars and is turned round an
angle of thirty degrees. Light going round a corner by instruments
adapted to show the result, and to measure the angles at which it is
turned, is called the diffraction of light.

I can show you an instrument which will measure the wave lengths of
light. Without proving the formula, let me tell it to you. A spirit
lamp with salt sprinkled on the wick gives very nearly homogeneous
light, that is to say, light all of one wave length, or all of the
same period. I have a little grating that I take in my hand. I look
through this grating, and see that candle before me. Close behind it
you see a blackened slip of wood with two white marks on it ten inches
asunder. The line on which they are marked is placed perpendicular
to the line at which I shall go from it. When I look at this salted
spirit lamp, I see a series of spectrums of yellow light. As I am
somewhat short-sighted, I am making my eye see with this eye-glass
and the natural lenses of the eye what a long-sighted person would
make out without an eye-glass. On that screen you saw a succession of
spectrums. I now look direct at the candle, and what do I see? I see a
succession of five or six brilliantly colored spectrums on each side
of the candle. But when I look at the salted spirit lamp, now I see
ten spectrums on one side and ten on the other, each of which is a
monochromatic band of light.

I will measure the wave lengths of light thus: I walk away to a
considerable distance, and look at the candle and marks. I see a set of
spectrums. The first white line is exactly behind the candle. I want
the first spectrum to the right of that white line to fall exactly on
the other white line, which is ten inches from the first. As I walk
away from it, I see it is now very near it; it is now on it. Now the
distance from my eye is to be measured, and the problem is again to
reduce feet to inches. The distance from the spectrum of the flame
to my eye is thirty-four feet nine inches. Mr. President, how many
inches is that? Four hundred and seventeen inches, in round numbers
420 inches. Then we have the proportion, as 420 is to 10 so is the
length from bar to bar of the grating to the wave length of sodium
light--that is to say, as forty-two is to one. The distance from bar to
bar is the four-hundredth of a centimeter; therefore the 42d part of
the four-hundredth of a centimeter is the required wave length, or the
16,800th of a centimeter is the wave length according to our simple,
and easy, and hasty experiment. The true wave length of sodium light,
according to the most accurate measurement, is about a 17,000th of a
centimeter, which differs by scarcely more than one per cent. from our
result!

The only apparatus you see is this little grating; it is a piece of
glass with four-tenths of an inch ruled with 400 fine lines. Any of you
who will take the trouble to buy one may measure the wave lengths of a
candle flame himself. I hope some of you will be induced to make the
experiment for yourselves.

If I put salt on the flame of a spirit lamp, what do I see through this
grating? I see merely a sharply defined yellow light, constituting
the spectrum of vaporized sodium, while from the candle flame I see
an exquisitely colored spectrum, far more beautiful than I showed you
on the screen. I see, in fact, a series of spectrums on the two sides
with the blue toward the candle flame and the red further out. I cannot
get one definite thing to measure from in the spectrum from the candle
flame as I can with the flame of a spirit lamp with the salt thrown on
it, which gives, as I have said, a simple yellow light. The highest
blue light I see in the candle flame is now exactly on the line. Now
measure to my eye; it is forty-four feet four inches, or 532 inches.
The length of this wave then is the 532d part of the four-hundredth
of a centimeter, which would be the 21,280th of a centimeter, say the
21,000th of a centimeter. Then measure for the red, and you would find
something like the 11,000th for the lowest of the red light.

Lastly, how do we know the frequency of vibration?

Why, by the velocity of light. How do we know that? We know it in a
number of different ways, which I cannot explain now because time
forbids. Take the velocity of light. It is 187,000 British statute
miles per second. But it is much better to take a kilometer for
the unit. That is about six-tenths of a mile. The velocity is very
accurately 300,000 kilometers per second; that is, 30,000,000,000
centimeters per second. Take the wave length as the 17,000th of a
centimeter, and you find the frequency of the sodium light to be 510
million million per second. There, then, you find a calculation of
the frequency from a simple observation which you can all make for
yourselves.

[Illustration: Vibrating Spherule Imbedded in an Elastic Solid.]

Lastly, I must tell you about the color of the blue sky which was
illustrated by the spherule embedded in an elastic solid. I want to
explain to you in two minutes the mode of vibrations. Take the simplest
plane-polarized light. Here is a spherule which is producing it in
an elastic solid. Imagine the solid to extend miles horizontally and
miles down, and imagine this spherule to vibrate up and down. It is
quite clear that it will make transverse vibrations similarly in all
horizontal directions. The plane of polarization is defined as a plane
perpendicular to the line of vibration. Thus, light produced by a
molecule vibrating up and down, as this red globe in the jelly before
you, is polarized in a horizontal plane because the vibrations are
vertical.

Here is another mode of vibrations. Let me twist this spherule in
the jelly as I am doing it, and that will produce vibrations, also
spreading out equally in all horizontal directions. When I twist this
globe round, it draws the jelly round with it; twist it rapidly back,
and the jelly flies back. By the inertia of the jelly the vibrations
spread in all directions, and the lines of vibration are horizontal
all through the jelly. Everywhere, miles away, that solid is placed
in vibration. You do not see it, but you must understand that they
are there. If it flies back it makes vibration, and we have waves of
horizontal vibrations traveling out in all directions from the exciting
molecule.

I am now causing the red globe to vibrate to and fro horizontally. That
will cause vibrations to be produced which will be parallel to the line
of motion at all places of the plane perpendicular to the range of the
exciting molecule. What makes the blue sky? These are exactly the
motions that make the blue light of the sky which is due to spherules
in the luminiferous ether, but little modified by the air. Think of the
sun near the horizon, think of the light of the sun streaming through
and giving you the azure blue and violet overhead. Think first of any
one particle of the sun, and think of it moving in such a way as to
give horizontal and vertical vibrations and what not of circular and
elliptic vibrations.

You see the blue sky in high pressure steam blown into the air; you
see it in the experiment of Tyndall's blue sky, in which a delicate
condensation of vapor gives rise to exactly the azure blue of the sky.

Now the motion of the luminiferous ether relatively to the spherule
gives rise to the same effect as would an opposite motion impressed
upon the spherule quite independently by an independent force. So you
may think of the blue color coming from the sky as being produced by to
and fro vibrations of matter in the air, which vibrates much as this
little globe vibrates embedded in the jelly.

The result in a general way is this: The light coming from the blue
sky is polarized in a plane through the sun, but the blue light of
the sky is complicated by a great number of circumstances, and one of
them is this: that the air is illuminated not only by the sun, but by
the earth. If we could get the earth covered by a black cloth, then we
could study the polarized light of the sky with simplicity, which we
cannot do now. There are, in nature, reflections from seas, and rocks,
and hills, and waters in an indefinitely complicated manner.

Let observers observe the blue sky not only in winter, when the earth
is covered with snow, but in summer, when it is covered with dark
green foliage. This will help to unravel the complicated phenomena
in question. But the azure blue of the sky is light produced by the
reaction on the vibrating ether of little spherules of water, of
perhaps a fifty-thousandth or a hundred-thousandth of a centimeter
diameter, or perhaps little motes, or lumps, or crystals of common
salt, or particles of dust, or germs of vegetable or animal species
wafted about in the air. Now what is the luminiferous ether? It is
matter prodigiously less dense than air, millions and millions and
millions of times less dense than air. We can form some sort of idea of
its limitations. We believe it is a real thing, with great rigidity in
comparison with its density, and it may be made to vibrate 400 million
million times per second, and yet with such rigidity as not to produce
the slightest resistance to any body going through it.

Going back to the illustration of the shoemaker's wax; if a cork will
in the course of a year push its way up through a plate of that wax
when placed under water, and if a lead bullet will penetrate downward
to the bottom, what is the law of the resistance? It clearly depends on
time. The cork slowly in the course of a year works its way up through
two inches of that substance; give it one or two thousand years to do
it, and the resistance will be enormously less; thus the motion of a
cork or bullet, at the rate of one inch in 2,000 years, may be compared
with that of the earth, moving at the rate of six times ninety-three
million miles a year, or nineteen miles per second, through the
luminiferous ether, but when we have a thing elastic like jelly and
yielding like pitch, surely we have a large and solid ground for our
faith in the speculative hypothesis of an elastic luminiferous ether,
which constitutes the wave theory of light.




THE LIMITATIONS OF SUBMARINE TELEGRAPHY.[8]


[8] Reproduced in abridged form from the _Electrical Review_ and the
cuts from _La Lumiere Electrique.--Science_.

The weight of the conductors, says Henry Vivarez in _La Lumiere
Electrique_, plays an important part in submarine telegraphy, not
merely as a heavy item in the outlay, but as one of the principal
factors in laying down the lines, and in taking them up in case of
damage. When the conductor is being raised, the grappling-irons which
lift it have to resist not merely the vertical component of the weight
of the cable, but also the considerable effects resulting from friction
against the water. It thus frequently happens, when working at great
depths, that the conductor may be exposed to a strain greater than it
is able to bear, and we are forced to have recourse to stratagems to
bring it to the surface. These artifices consist in the use of two or
more ships in raising, which is done as shown in Figs. 2 and 3, or, in
the most simple cases, with the aid of an auxiliary buoy, as in Fig. 4.
In any event, we see that the difficulties, and of course the cost of
raising, must be considerable.

[Illustration: Fig. 1.]

Hence to decrease the weight of the cables would be an important step
in advance. If the weight is in general very great, it is because the
copper core does not take any part in the strain which the entire
cable has to resist. We know, indeed, that copper cannot bear a
breaking-strain greater, at most, than 28 kilos per square millimeter.
Besides, it would be elongated by such a strain by a very considerable
fraction of its initial length; and, if the core were made to take
part in any manner whatever in the strain which the entire cable has
to support, it would be drawn out beyond its limit of elasticity, and
would remain permanently elongated, while the substances in which it is
inclosed would return to their natural length. It would result that,
being no longer able to find room in a sheath which had become too
short, the copper wire would take a sinuous form in its gutta-percha
envelope, and would occasion at certain points ruptures, the effect
of which would be to decentralize the wire, to perforate the layer of
insulating matter, and finally to open out a fault in the cable.

But there exists an alloy (silicium bronze) which can be drawn out into
wires having a conductivity equal to that of copper, and a mechanical
resistance equal to that of the best iron. The use of this alloy would
render it possible to set free the coating of the cables from a part of
the strain which it now has to resist, and to diminish, consequently,
their dimensions and weight. Wires are now made of this alloy, having
a conductivity of from ninety-seven to ninety-nine per cent. of the
standard, which at 0 deg.C., and with the diameter of a millimeter, have a
resistance of 20.57 ohms per kilometer. These wires do not break with a
less strain than from 45 to 48 kilos. per square millimeter, and, which
is a very precious property, their increase in length at the moment of
rupture does not exceed one or one and a half per cent.

Let us consider the deep-sea section of cable of the French company
from Paris to New York--the so-called "Pouyer-Quertier" cable,
constructed and laid in 1879 by Siemens Brothers of London.

The respective weight of each of its component elements is, per
nautical mile, copper core, 220 kilos; gutta-percha, 180 kilos;
hemp, or an equivalent, 80 kilos; 18 wires of galvanized iron of 2
millimeters in diameter, 860 kilos; external hemp and composition,
400 kilos; total, 1,740 kilos. Total diameter, 30 millimeters. Total
mechanical strength, 3,000 kilos, the wires of the covering being
supposed to be of iron. Weight under water, 450 kilos. It can support
its own weight without breaking for a length of from six to seven miles.

[Illustration: Fig. 2.]

The Atlantic presents from north to south, and at about an equal
distance from each continent, a sort of longitudinal ridge, in which
the depths vary from 300 to 400 meters. This ridge spreads out, in 50 deg.
north latitude, into the region which has received the principal wires
connecting England and France with the United States. On both coasts
there are depressions in which the bottom is at the depth of from 4,000
to 6,000 meters. The one on the east extends from the south point of
Ireland to the latitude of the Cape of Good Hope, and its left-hand
boundary follows the general outlines of the west coasts of Europe and
Africa. The two others, the northwestern and the southwestern, form two
basins, bordering respectively on the United States and the Antilles
and South America.

In these depressions soundings have shown certain zones in which the
depths exceed 6,000 meters, the principal of which are found to the
west of the Canaries, to the south of Newfoundland, between Porto Rico
and the Bermudas, and to the right of the Isle of Marten-Vaz.

[Illustration: Fig. 3.]

The great depths of the Pacific are differently distributed. Between
Japan and California, between 40 deg. and 50 deg. north latitude, there is the
Tuscarora depression, which has depths of from 6,000 to 8,000 meters.
Parallel to Japan and the Kuriles there is a depression in which has
been found the greatest known depth--8,513 meters.

We see, therefore, that any new great submarine line, having to extend
into another zone than that which has received the present Atlantic
cables, must traverse depressions in which the bottom reaches a maximum
depth of 4,000 meters. The possibility of raising a damaged cable
would be very problematical under such conditions, and it would become
certainly impossible in case of a cable from San Francisco to Japan.

Under these conditions, we are forced to conclude that the use of the
present cables limits strikingly the progress of submarine telegraphy,
which must remain confined to certain zones of the Atlantic, to inland
seas, and to lines along the coasts. But if we consider the daily
progress of applied science, and the constantly increasing demand for
rapid communication between nations, it is certain that we must shortly
undertake the study of new cables intended to traverse the greatest
depths of the ocean for long distances. Necessity, therefore, compels
us to investigate the new solutions of the problem, which may furnish
us with light cables, easy to lay, and possible to repair.

[Illustration: Fig. 4.]

A cable made by Mr. J. Richards is composed as follows: core of
silicium bronze equal in weight to that of the Pouyer-Quertier cable,
or, per nautical mile, 220 kilos; gutta-percha, 180 kilos; layer of
hemp, 80 kilos. The sheathing is formed of 28 wires of galvanized
iron of 1.25 millimeters in diameter, each covered with hemp, and all
twisted into a rope around the dielectric; the wires, 500 kilos: the
hemp covering them, 250 kilos. The weight of the cable is, therefore,
1,230 kilos in the air, and 320 kilos in the water. Its diameter is 25
centimeters, and its resistance to fracture 2,800 kilos, of which the
core supports one-half. Under these conditions, the cable can support
from eight to nine nautical miles of its length, and can be raised from
the greatest depths. The results of this comparative examination are
self-evident.

For an equal conductivity and an approximately equal mechanical
strength, the new cable is in weight and bulk equal to about two-thirds
of the Pouyer-Quertier cable. It would cost about $165 less per mile,
and would require, for laying, a ship and engines of less power,
and therefore cheaper. The reduced armature will suffice to resist
friction and the attacks of animal life in the deep sea; but for the
shore ends we must keep to the types generally employed. Such as
it is, and although it may undergo modifications in detail from a
more complete study and from experience, it merits the attention of
competent engineers.




WILLIAMS' SYSTEM OF COAST DEFENSE BY ELECTRICAL TORPEDOES.


Our adjoining engravings illustrate the system of J. S. Williams, for
working electrical torpedoes, launches, and torpedo boats, and the
appliances be proposes for their equipment and his method of utilizing
a system of electrical appliances for the defense of sea-ports,
harbors, coast, and coaling stations. We use Mr. Williams' own words
in describing this invention. Fig. 1 illustrates men-of-war or vessels
attempting to force their way into a harbor defended by such means.
The movable and controllable torpedoes are indicated by letters of
reference, A, connected through the medium of paying-out electrical
cables, G, with the base of operations upon the shore at C, and the
launches and floating torpedo batteries or vessels, D. Several lines of
torpedo defense or attack are shown, and illustrate the hostile vessels
coming within the destructive radius of the movable and controllable
torpedoes, which radius is limited only by the length of the paying-out
cable, which length can be 1-1/2 miles (more or less). These means secure
an effective weapon at all times under command from the base of
operations over a radius of 1-1/2 miles, as against a radius of 50 ft.,
which is the estimated effective range of destruction for fixed mines
containing an equal explosive charge.

The movable torpedoes operated from the shore can be supplied with
electric power from the main circuits extending along the coast from
the developing source, at any distance from the electric power station
or base from which the movable torpedoes are operated or supplied. Any
natural force, fuel, or other means can be employed for the development
of the electric force, which can be transmitted through the main
circuits with high tension or pressure to the power stations along
the coast, or to the floating magazines, where electric accumulators
are placed to hold a reserve of energy. The accumulators at such
stations can be compounded so as to be at all times ready for supplying
power, and being charged, except when the limit of storage is reached.
Electric cut-offs are provided in the loop or derived circuits from the
main to cut the magazines out of the circuit when such predetermined
limit of energy is in reserve, and means are employed to prevent the
backward flow of the current toward the source from the power stations
supplied from the main or other circuit. Means are also employed to
automatically regulate and prevent any excess of current passing
through the circuit in which the accumulators are included. The
discharging circuits from the reserve magazines can be connected at
the will of an operator with an electric circuit, including electric
magazines, forming part of the equipment of the launches, vessels,
or torpedoes, so as to supply electric power thereto. This can be
accomplished at the wharves or through the medium of a cable buoyed
along the coast, so as to obviate the necessity of the launches or
vessels returning or running into harbor. Signaling devices can extend
from such buoy to the operator along the shore, who will close the
circuit from the reserve or main supply circuit. Fig. 2 illustrates a
sectional elevation of an electrical torpedo provided with mechanism
at the stern for operating the rudder electrically, and the force is
regulated by an automatic or manually operative variable resistance
interposed in the electrical circuit at the switch board of the cable.
A circuit reverser and variable resistance are arranged upon the switch
board, so that the operator at the base can change the direction of
the current, and regulate the force applied through the medium of the
electrical cable in such a manner as to adjust the rudder to port or
starboard, and, if so arranged, to maintain it at any angle by varying
the resistance in the circuit. The rudder mechanism can be operated
by the electric energy stored on board the torpedo through the medium
of an electric circuit thereto from the electric accumulator provided
with a circuit closer and variable resistance worked by the force
passed through the paying-out cable. The force passing there through is
regulated by a pressure regulator and controlled by a circuit reverser
and variable resistance upon the keyboard. Means are also employed
for indicating to the operator the position of the rudder at any
moment, and such position will correspond to some defined resistance
introduced at any given moment in the circuit. The mechanism combined
with the rudder can consist of an arrangement of compound solenoids,
the armatures of which are connected to a lever on the rudder head, or
a small electric motor can be employed for operating worm gearing in,
or combined with, the rudder head. The rudder is brought back to the
midship or normal position by springs or counterbalance weights.

[Illustration: FIG. 1

--FIG. 3--

--FIG. 4--

--FIG. 5--

--FIG. 6--

--FIG. 2--

WILLIAMS' SYSTEM OF COAST DEFENSE BY ELECTRICAL TORPEDOES.]

The motor of the torpedo, as illustrated, is composed of a number of
disk-shaped armatures fastened on the shaft, combined with the screw
propeller; the field magnets, being also of disk form, are arranged so
that the armatures revolve within close proximity, but not touching the
pole surfaces. This enables an exceedingly high efficiency and great
power to be realized from a motor of light weight. This construction of
motor is specially suitable for use in the equipment of torpedoes and
launches, and permits an increase of the power of the motor in either
of two directions, i. e., either by increasing the number of disks of
a given diameter upon the shaft, or by increasing the diameter of the
disks, both of these methods giving increased power in direct ratio
to the increase of size. The accumulator or secondary battery, c, is
especially designed to store the energy in a small space, and with
light weight, and so as to command an amount of energy representing
the power necessary for a speed of 25 miles an hour or more. In the
electrical circuit, between the motor and accumulator, variable
resistances and other governing devices are interposed, by which the
current passing to the motor is regulated automatically in accordance
with the speed of the motor, or with the electric pressure in the
circuit from the accumulator. A circuit closer or variable resistance
operating in the circuit is connected by the cable with a variable
resistance at the switch board, and operated by the current controlled
thereby. The force to the motor can be regulated, controlled, or
stopped at the will of the manipulator at the switch board placed at
the point from which the torpedo is dispatched. Signaling devices or
guide rods, O, for indicating the position and direction of movement
of the torpedo to the operator can be arranged to be raised and
lowered, through the medium of electrical appliances, P, at will, by
a current sent through the paying-out cable from the keyboard at the
base of operations. Fixed means or sight rods can be used, and hooded
incandescent lamps, O_{2}, can be carried by the signal or sight rods,
by which means at night or in the day the operator will be enabled to
direct the torpedo to the object of attack in spite of adverse or cross
currents, or a change in the position of the vessel under attack.

The body of the torpedo containing the machinery and explosive can be
arranged to be any desired depth below the surface of the water, and be
supported by a buoy as a shield, or be covered by a protection against
shot, the displacement of the torpedo being regulated in accordance
with the means employed for maintaining it the desired distance below
the surface. The torpedo can be ballasted and provided with fins
to offer the necessary resistance to the action of the propelling
machinery. The electrical paying-out cable, G, is shown in a coil in
proximity to the chamber at the bow, which is designed to carry the
explosive charge in a fixed or detachable magazine, arranged when
detachable to drop a determined distance, and to be fired electrically
by the operator or automatically.

Fig. 6 illustrates an apparatus in which a dynamo is operated by a
rotary engine having a throttling device controlled electrically by
the current passing through the discharging circuit of the generator;
the circuit of the generator is connected with the paying-out cable of
the torpedo, through the medium of the key board, in which a variable
resistance and regulating devices are employed for controlling the
operation of the torpedo. Electric magazines are shown arranged
to operate in the discharging circuit of the generator, and to be
connected with the appliances forming part of the equipment of the
torpedo through the medium of the paying-out cable, in conjunction
with which is arranged the circuit-closing devices of the switch board
under the control of the operator at the stations. Automatic electric
pressure regulators are used in the circuit from the source, so as
to reduce or regulate the pressure to some predetermined limit. The
circuit controllers and manually operative variable resistances upon
the switch or keyboard can have indicators connected with them. Under
such conditions, with the circuits and appliances upon the torpedo
constructed to a known standard, the control of such torpedo in all
its movements and operations is easy and certain. Such appliances
are especially designed for use upon men-of-war or steam or electric
launches when the torpedo vessels are not equipped with electrical
magazines. Fig. 5 illustrates a floating fort or battery equipped with
machinery, electrical apparatus, and torpedoes, as illustrated in Figs.
2 and 6. The floating fort or battery equipped with electrical or other
machinery for propelling can be anchored in suitable positions, or
moved from place to place to be in torpedo range of a fleet, or in a
suitable position for supplying torpedo launches with torpedoes, and
electric or other means of power.

Fig. 3 illustrates a steam launch, and Fig. 4 an electric launch
fitted with electrical appliances and compartments containing a means
for carrying and discharging electrical torpedoes. By the employment
of such means, and a well-organized system of coast defense, it will
be practically impossible for hostile vessels to land troops, or to
inflict a serious damage upon shipping or seaport towns. Any extent
of coast or estuary can be thoroughly protected by launches, light
vessels, and appliances operated from fixed electrical stations,
supplied with power and means of operation from any point, however
distant. For carrying such a system into practical operation, the cost
will, it is claimed, be but a tithe of what would be required for
placing an inefficient system of fixed mines and forts, or for building
men-of-war for coast defense, as men-of-war are practically defenseless
against a greater number of high-speed launches equipped with movable
and controllable torpedoes, the reasons for which are obvious, as a
sufficient number of such launches would cover a greater distinctive
range than the vessel which depended upon the range of its guns, or
those combined with uncontrollable torpedoes.




NEW ELECTRIC GAS LIGHTER.


Let not the epithet "Perpetual," which the inventor applies to the
little apparatus that we are about to describe, frighten the reader,
for its only purpose is to indicate that the instrument in question is
capable of operating indefinitely, without care and without there ever
being any need of taking it apart.

[Illustration: Fig. 1--PERPETUAL GAS LIGHTER.]

In this gas lighter the inflammation is produced by a small spark,
but this latter, instead of being obtained by means of a pile, which,
after a certain length of time, has to be mounted anew or entirely
renewed, is secured by borrowing the energy produced by the operator
pressing upon a button. It is, then, in reality, a _mechanical_
lighter in which electricity intervenes as an intermedium charged
with the transformation of work into sufficient of a spark to produce
inflammation. Thanks to this principle, and to the arrangement of the
apparatus, there is secured cleanness, safety, and economy.

The lighting is reduced, then, to opening the cock and placing the
extremity of the rod over the burner, or over the edge of the glass
in burners provided with a chimney. Upon pressing the button and then
freeing it, a spark leaps between the two points and lights the gas.
(Fig. 1.)

[Illustration: Fig. 2.--A, cylinder with lighting rod, G. B, movable
cylinder fixed upon the axis, E. D, handle containing a rack actuated
by a button, F.]

The electric generator is a static induction machine of very small
size, and the arrangement of which will be understood by reference to
Fig. 1, which gives a general view of the apparatus with a portion
removed in order to show the relative position of the different parts,
and to Fig. 2, which shows the latter detached. A is an ebonite
cylinder containing the entire machine, and closed above by a cap of
the same substance upon which is screwed the lighting rod. The cap is
traversed by conducting wires which end in two contact springs that
establish an electric communication with the lighting tube.

Two inducting armatures of tin are cemented to the interior of
the cylinder, A, and occupy, each of them, about a third of its
circumference. The bottom of the cylinder, A, supports six contact
springs, parallel with each other and constituting three distinct pairs
which are properly connected, two by two, with the different parts of
the rest of the apparatus.

The movable or induced cylinder, B, of ebonite is provided with six
equidistant and insulated thin sheets of tin of a width nearly equal
to the interval which separates them. This cylinder is given a rapid
rotary motion by means of a system of rack and gearing every time the
button, F, is pressed. During the revolution of the cylinder the six
insulated plates come successively into communication with the six
springs, and these put them successively in communication, two by two,
first with the fixed inducting armatures, second, with the conductors
connected with the two points between which the spark is to pass, and,
third, with each other.

The apparatus operates, then, like Sir William Thomson's replenisher.
It is only necessary for the armatures upon the cylinder, A, to be at
the start at a difference of potential as small as desirable to suppose
it, in order to have the play of the machine multiply the charge and
soon give it sufficient tension to cross the interval that separates
the two points fixed at the extremity of the lighting rod, G. From a
technical point of view, the ingenious and new idea resides in the
application of a multiplier of charges with which the priming and
operation are always secured, provided the insulating parts are so dry
that the losses due to dampness are inferior to the machine's power of
production. This result, moreover, is easily attained by the use of a
hermetically closed system, and of drying substances placed in that
part of the cylinder which forms the handle of the apparatus.

From a mechanical point of view, the lighter contains a series of
practical and simple arrangements which make it an apparatus at once
convenient, strong, and sufficiently perpetual, as regards duration,
to partially justify the name that has been bestowed upon it by its
inventor, Mr. J. Ullmann.--_La Nature_.




INSULATORS FOR TELEGRAPH AND TELEPHONE LINES.


In the accompanying cut we bring together a few figures of porcelain
insulators for uncovered wires placed inside or outside of houses.

[Illustration: PORCELAIN INSULATORS FOR TELEGRAPH AND TELEPHONE LINES.]

Figs. 1 and 2 represent simple and double channeled pulleys to be
fixed against a wall, or upon a pole or a door post, by means of nails
simply. Fig. 3 shows a pulley of larger dimensions for iron wires.
Figs. 4, 5, and 6 show perforated insulators, that are quite convenient
for holding and supporting a wire, but which are not convenient to put
in position when the wire is of some length. Fig. 7 shows a device for
protecting a wire that passes through a wall. Fig. 8 shows a support
designed especially for small poles. It may be used either by passing
the wires through the aperture or winding it around the neck of the
bell. Fig. 8 shows a cleft insulator designed especially for fixing a
wire in places where it must form an angle.--_La Nature_.




ELECTRIC LIGHT IN THEATERS.


M. Brandt places alternately, in a continuous line, forty lamps of
ordinary glass, forty of green glass, and forty of red glass, making
a hundred and twenty lamps in all, at the foot of the stage. Each
series of forty lamps forms a separate circuit. The three series can
be lighted independently, or they may be combined, in order to obtain
different effects of color. For example, a delicate rose hue may be
produced by simultaneously lighting the red and the white lamps; a
moonlight effect, by a combination of the white and the green lamps.
In order to pass gradually from the latter to full daylight, it is
only necessary to increase the resistance in the green circuit while
strengthening the current in the white lamps. Moreover, the two sides
of the stage may be lighted independently, because the 120 lamps are
again subdivided into two circuits of sixty each. We may thus have a
moonlight on one side of the stage, while the other side, at the moment
when an actor enters with a torch in his hand, seems to be illuminated
by the reflection from the torch. When the footlights are of gas, a
current of hot air ascends above the whole line of lights, forming a
sort of gaseous wall between the stage and the audience, which often
makes it difficult to hear the actors. This inconvenience is suppressed
by electric lighting, and the opera singers are agreeably surprised at
the great improvement.--_Lumiere Electr._




THE NEW DAM AT SURESNES.


It was not till 1867, on the occasion of the Universal Exhibition,
that a dam was constructed at Suresnes that permitted of omnibus-boat
service. The effect that this dam had was to raise the water 7-1/2 feet up
stream, and to consequently suppress the natural incline of the river
between Paris and Suresnes. Its action made itself felt as far as to
the Austerlitz Bridge in front of the Garden of Plants.

Between Suresnes and Lavallois the Seine is divided into two arms
that are separated by the isles of Puteaux and Grande-Jabbe. The left
arm was dammed at Suresnes, and here was established the sluice that
allowed boats to cross the falls. The right arm was dammed at Levallois.

A law of April 6, 1878, decided the increase of the depth of the Seine
between Paris and Rouen in order to allow boats of a draught of ten
feet to reach Paris, and to bring thither, without transfer, English
coal and Bordeaux wines. The Consul-General of the Seine having offered
to contribute toward the expense, on condition that such boats might
have it in their power to ascend as far as to Bercy, a law of July 21,
1880, decided that the Suresnes dam should be raised about three feet
in order to increase the anchorage. To effect this, the dams of 1867
were entirely rebuilt, the new ones being located at Suresnes, across
the two arms of the river. At the same time, the existing sluice was
doubled by another one that was larger and deeper.

This great work was executed under the able direction of Mr. Boule,
engineer in chief of roads and bridges, who has in charge the
navigation of the Seine, outside of Paris, between Montereau and
Poissy. The new sluice was constructed in 1880 and 1881, the dam to the
left and the intermediate weir in 1882 and 1883, and the pass to the
right in 1884. The width of the Seine at this point is about 820 feet,
the length of the passes varies between 209 and 236 feet, and the two
sluices occupy a width of 98 feet.

In the construction of the three passes there were established, up and
down stream, dikes about 325 feet apart, thus giving considerable space
for the installation of work yards, and much facilitating operations.

The new dam is closed by movable mechanisms of the kind invented by
Engineer Poiret in 1834. The iron trestles that support the wickets are
the largest that have ever been constructed, their height being nearly
20 feet and their weight 3,950 pounds. During freshets they are laid
upon the bed of the sluice, and when the water subsides they are raised
vertically. Upon these supports are placed swinging wickets, like those
of mills, according to a system devised by Mr. Boulet in 1874, and
which has been tried since then with success at the Port-a-l'Anglais
dam near Paris. This system has likewise been successfully applied upon
the Moskowa, below Moscow, and upon the Saone, at the Mulatiere dam,
near Lyons.[9]

[9] See SUPPLEMENT No. 264 for an illustrated description.

The construction of the new sluice presented great difficulties,
by reason of the fact that it was necessary to avoid obstructing
navigation in the existing sluice, where the boats stood thirteen or
fifteen feet above the laborers who were working at the side, behind
simple dikes. Yet it became necessary to forbid the passage of the
sluices for nearly a month each year. At Suresnes this was taken
advantage of each time to keep the works in full blast during the
whole night, the lighting being done by electricity. During these
interruptions the boats accumulated at the sides of the dam, and gave
the public an idea of what Paris would be as a sea port.

All the work is now finished. Its estimated cost is six millions, two
of which were devoted to the construction of about half a mile of dock
wall and of a long and wide sewer.

The sluices were opened for navigation on the 15th of September last.
The new dams will be in operation in 1885, and next summer they will
increase the height of water in Paris by one meter.--_L'Illustration_.

[Illustration: IMPROVEMENT OF THE RIVER SEINE.--THE NEW DAM AT
SURESNES.]




BREAREY'S AERONAUTICAL MACHINE.


Mr. Fred. W. Brearey has been the honorary secretary of the
Aeronautical Society of Great Britain ever since its establishment in
1866. In the course of his experiments, extending over some years, he
found that if a serpentine action were imparted to a fabric it would
propel an attached object many times its weight in the air. He records
in his published magazine articles that he took the idea from watching
the movements of a skate in an aquarium, which in swimming undulated
its whole body.

[Illustration: BREAREY'S FLYING MACHINE.]

In applying the principle to locomotion in air, it is of course
impossible to undulate what may called the backbone of the whole
structure in the manner of the skate. But a fabric may be so attached
to a receptacle, and so worked from thence by a suitable motive power,
that its undulations will propel and support a considerable weight,
depending upon the energy with which such fabric is thrown into waves.
He believes that the awning of a vessel can be made in this way to
contribute to a ship's progress at the same time that it would cool the
passengers.

Mr. Brearey argues that the instinct of the bird enables it to
adapt itself instantaneously to varying circumstances; that in any
arrangement for effecting flight by machinery--the adjustment of
parts to meet sudden requirements being a matter requiring momentary
thought--it is desirable, if practicable, to employ large surfaces
for parachutic action, at the same time making this means of safety
not an incumbrance, but an aid. The possession of instinct allows of
the employment of the smallest surface in proportion to weight; the
possession of forethought renders it necessary that intermittent action
shall be safeguarded by large surfaces.

This requirement is fully met, the inventor says, by the arrangement
advocated by him, and none but edge resistance is offered to the air,
except the sharp lines of the necessary vehicle. The manufacture of
such an apparatus upon a scale of utility would be as follows:

A flat-bottomed receptacle, somewhat of boat shape, would be fixed
upon wheels. At the fore part of the boat a motor would from each side
elevate and depress two wing-arms, each 15 ft. long. (See Figure.)
Along the wing-arms is attached a fabric which would form the front
part of a kite, which, being fastened in the center to the edge of
the boat, would continue for 15 ft. to the rear, being extended about
6 ft. farther than the stern of the boat by a continuing spar. To a
cross piece here would be fastened the tail end of the kite, which,
however, instead of a point, would be about 5 ft. in width. From this
again would extend a tail of about 12 ft., to which either a lateral,
twisting, or a vertical movement could be imparted by cords in the
hands of the operator in the boat for steering purposes. From the fore
part of the boat would extend a bowsprit, from which cords would be
attached to the two wing-arms to prevent the weight of the fabric from
dragging them backward.

An important arrangement has been adopted by the inventor, which he
calls the pectoral cord, which by its automatic action assumes the
functions of the pectoral muscle of the bird. This is an India-rubber
cord. It is attached by its two extremities to the under portion of
each wing-arm, and in models passes underneath a central shaft--in
this case the boat. Its degree of elasticity is regulated by the
weight. When any model with wings is committed to the action of the
air, the pressure of the air causes the wings to fly upward, and power
is required according to the weight sustained to depress the wings
against the weight. The strength of the cord, however, is such that it
maintains the outstretched wings at that angle which is suitable for
gliding upon the air without, in the case of the bird, any enforced
muscular exertion. The contraction of this cord assists the power
exerted in the downward stroke.

The wing arms would not be rigid throughout their length. They would
consist of a number of rattans or canes firmly bound together by close
wrapping, and tapered by cutting off one at intervals, this being
practically unbreakable by any accident likely to occur. The portion
next to the body for 5 ft. or 6 ft. might be stiffened by a steel tube,
forming the center round which the rattans are wrapped. By this method
of forming the wing-arms their length may be increased at pleasure.

A small model upon this principle, but without any motive power, was
liberated as an experiment by Captain Templer, from a balloon which had
risen 200 ft. or 300 ft. from Woolwich Arsenal, and it traveled back
again to the arsenal half a mile against the wind uninjured.

The importance of such an apparatus might become manifest in any flight
of a balloon from a besieged place over the heads of an investing army.
The results of a rapid survey of the enemy's positions could be written
and dispatched from a height against the same current which wafted the
balloon, so as to fall within the lines of the besieged.

Given a light motive power, which it is hoped may soon be forthcoming,
Mr. Brearey anticipates the action of the machine as follows:

A surface will be provided according to the weight to be carried, the
supporting surface of a parachute being known. Upon being run down an
incline the envelope will be inflated by the pressure of the air, and
the wing arms raised to that point where their further elevation is
restrained by the pectoral cord. The machine will then naturally float
away from the incline, and the occupant must set his motor in action.
The downward blow of the wing-arms will cause the fabric immediately
attached thereto to imprison a mass of compressed air, and the
following wave will force it along the under side of the fabric. This
will cause propulsion.

The return or up stroke cuts off and diverts from the upper part that
air which, but for the rise of the wing-arms, would flow over the back,
and shunts it underneath, while that which is embraced in the concave
fabric following the up-stroke is thrown off in a wave to the rear
above the machine, and so on alternately.

During this energetic action the whole fabric is kept in a state
of corrugation, and to such extent is rigid. It possesses all the
properties of a plane, and superiority over a plane, inasmuch as it
propels itself, and upon cessation of action assumes the functions of a
parachute, the descent of which a man may regulate by a step backward
or forward.

The latest invention which has been completed upon a full scale is the
idea of Mr. H. C. Linfield, of Margate. It is really a plane-propelling
machine, but the planes are compressed, it may be said, into small
compass, being only two inches apart, and being of such number and
extent as to present 438 square feet of strained and varnished linen in
two frames, each five feet square. The dimensions of the machine are 20
ft. 9 in. in length, 15 ft. in width, and 8 ft. 3 ins. in height. It
runs upon four wheels; the two front wheels are 6 ft. in diameter, the
two hind wheels 3 ft. The frames before mentioned are fixed one on each
outer side of the front wheel at an upward angle. The wheels have been
tested to sustain a weight of 5 cwt.

The weight of the machine is 240 lb., and of its inventor 180 lb.
He sits between the wheels and works two treadles, which actuate a
nine-bladed screw 7 ft. in diameter, fixed in front of the machine, to
which he can impart 112 revolutions per minute. This suffices to enable
him to travel along a level road.




RAISING OF THE FALLEN GIRDER OF THE DOUARNENEZ VIADUCT.


During the erection of the viaduct at Douarnenez--Department of
Finistere--over the river Pouldavid, one end of one of the heavy
latticework girders dropped into the river, as shown in the upper
one of the annexed cuts taken from _L'Illustration_. The difficult
problem to be solved was to remove the obstruction in as short a time
as possible, and at the least expense; and the engineers came to the
conclusion that it would be best to raise the fallen end, as the girder
was intact, with the exception of those parts that struck the bottom of
the river, and which could easily be replaced by others.

[Illustration: THE VIADUCT OF DOUARNENEZ.--THE POSITION OF THE FALLEN
GIRDER.]

[Illustration: THE VIADUCT OF DOUARNENEZ.--THE GIRDER RAISED.]

The viaduct has three spans of 190 ft. each, and is 88 ft. above the
surface of the water. While rolling the girders upon the piers, the
pivot of one of the rollers broke, and a projecting length of 183 ft.
of the girder dropped a vertical distance of 72 ft. That part of the
girder that had to be raised was 183 ft. long, and weighed 145 tons,
and the free end had to be moved a distance of 72 ft. in an arc the
radius of which was 183 ft. Suitable scaffoldings were erected on the
piers and below the fallen end of the girder; four strong and heavy
double chains were connected with the lower end of the girder and
passed over a scaffolding erected for this purpose, and the opposite
ends of the chains were connected with a heavy box weighted with rails,
and containing 2,700 cubic ft. of water. The upper end of the fallen
girder was disconnected from the other parts of the structure, and a
heavy steel pivot bar inserted, upon which the girder could turn. The
box was so weighted that the fallen girder was somewhat heavier than
the box, and then windlass chains were connected with the lower end
of the girder, and wound upon windlass drums operated on top of the
scaffolding. The weighted box thus merely acted as a counterbalancing
weight, the raising being accomplished by means of the windlass. On
the 1st of August the lower end of the girder was raised 17 inches,
and remained in this position for twenty-four hours, during which time
examinations were made which proved that the calculations were correct,
and that all the parts worked perfectly. The operation was completed
the next day with perfect success, and was witnessed by a great
multitude, attracted by the novel sight.




IMPROVED WIRE TESTING MACHINE.


The illustration represents a multiple wire tester, constructed for the
Trenton Iron and Steel Company by Riehle Bros., of Philadelphia. It
consists of a weighing mechanism (seen on the left, with a capacity of
4,000 pounds), two single or alternating pumps, a hydraulic jack, a
patented three-way valve, and a rising and falling accumulator.

The weighing end of the machine, placed horizontally and secured by
bolts to a foundation, is accurate, and will weigh the strain on one to
six wires at a time. It is provided with self-adjusting grips to take
in wires from No. 10 to No. 16, and hold them firmly. It can be adapted
to take in a larger or smaller range of numbers when desired. There is
a set of gripping appliances at both ends, and in the present instance
they are 90 feet apart--one set at the scale end, and the other secured
to head of piston. The jack is 5 feet in length, and lined with brass;
its outside diameter is 3-1/2 inches; its inside diameter, 2-1/4 inches. Like
the scale end, it is firmly bolted down to its foundations.

The plunger has a stroke of 4 feet. It is supported and guided by three
guides, the top one being a straight tube running on turned rollers. A
three-way valve controls the movements of the jack and accumulator, and
supplies water to the jack by a lever. When the lever is raised, the
water is forced into the larger area of the jack, causing the plunger
to move backward and bring a strain on to the wires or other specimens;
when the lever is lowered, the water in the larger area of the jack
only returns to the reservoir of the pump (to be used again). Now,
without changing the position of the lever, the plunger will return
automatically, without weight or counterbalance, with a steady, smooth,
and uniform motion.

The pump has a slow motion, 60 revolutions per minute. It has two
single action pistons, and the valves are so simple and readily
accessible that an ordinary mechanic can examine and repair, when
necessary, in a short time. The accumulator is so arranged as to
overflow when it comes to its maximum height. The machine can be
adapted to stretching and straightening wires in lengths to a given
amount.

The weight on the scale and that on the accumulator is made to
correspond, so that wires of a certain number or size can be quickly
tested in quantities under exactly the same conditions, with only the
movement of the lever.

[Illustration: IMPROVED WIRE TESTING MACHINE.]




IMPROVED DOUBLING AND LAYING MACHINE.


The tenacity with which whip cord, cotton cord, and other similar
lines preserve their twist when properly made, is a little remarkable
when considered in relation to the materials from which they are
manufactured, and which as a rule show a tendency when ordinarily
twisted to return to a straight line. This was one of the reflections
which occurred to us when watching a James doubling and laying machine
at work at the late Textile Exhibition, on the stand of Walter T.
Glover & Co., of Manchester. We give a perspective view of this machine.

[Illustration: IMPROVED DOUBLING AND LAYING MACHINE.]

There are several ways of carrying out the process of doubling, which
in its simplest sense consists in laying a given number of folds of
yarn together and putting a twist into them. But beyond this we come to
spindle banding, which is cord, or rope in miniature, and it is made
of three or more ends of the doubled yarn just mentioned, such doubled
yarn becoming, in fact, the strand of a small rope. To lay these
strands properly into a cord they should not only be twisted together,
but each should be twisted separately in the opposite direction to
the twist of the cord. A banding machine, therefore, has to impart
a double twist, and to perform the work perfectly each twist should
be capable of easy regulation; and the drag upon the bobbins should
admit of being adjusted to requirements. These conditions are met in
the James machine, as evidenced by the samples of work produced by it.
As shown in our engraving, the apparatus consists of three heads, of
four spindles each, being capable therefore of doubling a four-strand
cord. The heads work independently of each other, and by throwing one
or two of the spindles out of action a three-strand or a two-strand
cord will be produced. The cord is twisted regularly, and may be made
continuously to any length. The uniformity of the twist depends upon
the fact that the cord is taken up at a regular rate, by a simple and
neat motion, consisting merely of a pair of pulleys, one grooved and
the other with a roughened surface. After leaving these, the cord is
coiled upon the reels seen on the top of the framework. The twist given
to the cord depends upon the rate at which it is taken up, the speed
of the center spindle remaining constant. The twist in the strands is
governed by the speed at which the bobbin spindles revolve. This may
be adjusted as required, by a series of change wheels. An effective
stop motion is also applied to automatically stop the head in which a
breakage takes place, whether of the cord itself or of a single strand.
Either head is started by depressing the handle or knob in front of it.
A feature for which particular merit is claimed is that a heavy drag is
put upon all the strands separately for the purpose of taking out all
the stretch before twisting, which is an important desideratum for the
production of good banding. This is accomplished by hanging weights on
the spindles, which cause the strands to be twisted under tension. The
tension is altered as required by the size and nature of the yarn, by
removing or adding to the weights. The heads being independent of each
other enables the machine to be employed on three cords of different
material and thickness. The production is about 1,300 yards per head
for ten hours, and it is stated that a girl can mind as many as 80 or
90 heads.--_Iron._




BOILER TUBES.


The following table gives the draught area and heating surface of the
various sized boiler tubes and flues:

  ----------+---------------+-------------+----------------+-------------+
            |               |             |                | No. of      |
            |               |             |Heating surface | tubes in 1  |
  External  |Draught area   |Draught Area |in feet         | sq. foot of |
  Diameter. |in sq. inches. |in sq. feet. |per ft. of tube | draught     |
            |               |             |in length.      | area.       |
  ----------+---------------+-------------+----------------+-------------+
  5/8       |     ......    |   ......    |     .1636      |    .....    |
  3/4         |     ......    |   ......    |     .1963      |    .....    |
  1         |       .575    |    .0040    |     .2618      |    250.0    |
  1-1/4        |       .968    |    .0067    |     .3272      |    149.3    |
  1-1/2        |      1.389    |    .00964   |     .3927      |    103.7    |
  1-3/4        |      1.911    |    .0133    |     .4581      |     75.2    |
  2         |      2.573    |    .0179    |     .5236      |     55.9    |
  2-1/4        |      3.333    |    .0231    |     .5891      |     43.3    |
  2-1/2        |      4.083    |    .0284    |     .6545      |     35.2    |
  2-3/4        |      5.027    |    .0349    |     .7200      |     28.7    |
  3         |      6.070    |    .0422    |     .7854      |     23.7    |
  3-1/4        |      7.116    |    .0494    |     .8508      |     20.2    |
  3-1/2        |      8.347    |    .0580    |     .9163      |     17.2    |
  3-3/4        |      9.676    |    .0672    |     .9818      |     14.9    |
  4         |     10.93     |    .0759    |    1.0472      |     13.2    |
  4-1/2        |     14.05     |    .0996    |    1.1781      |     10.2    |
  5         |     17.35     |    .1205    |    1.3090      |      8.3    |
  6         |     25.25     |    .1753    |    1.5708      |      5.7    |
  7         |     34.94     |    .2426    |    1.8326      |      4.1    |
  8         |     46.20     |    .3208    |    2.0944      |      3.1    |
  9         |     58.63     |    .4072    |    2.3562      |      2.5    |
  10        |     72.23     |    .5016    |    2.6180      |      2.0    |
  ----------+---------------+-------------+----------------+-------------+




IMPROVED LADLE CARRIAGE.


We give below two views of a ladle carriage which has been constructed
from the designs of Mr. Thomas Wood, the chief engineer to the Ebbw
Vale Steel, Iron, and Coal Company. These works cover a large extent of
ground, the Victoria furnaces and the Ebbw Vale furnaces, both of which
supply one steel plant, being over a mile apart. Although this gives
a long distance over which the molten metal from the furnaces has to
be carried, it is by no means unprecedented; the Barrow furnaces for
instance being situated still further from the steel works they supply.
Until a short time ago, however, the Ebbw Vale Company had their
Sirhowy furnaces in blast. These are, or rather were, for now they
are dismantled, situated six miles by rail from the converters they
supplied at Ebbw Vale, consequently the ladle containing the 10 tons of
molten metal had to be brought this distance each time the converters
were charged. In order to meet the exigencies of such a service, the
ladle carriage we now illustrate was designed by Mr. Wood.

By means of the gearing of wormwheel, rack, and pinion, which are
clearly shown in Fig. 2, the ladle can be retained in the center of the
carriage and kept upright for running; a clip which is easily knocked
out of gear being fitted to retain it in the necessary position. When
the ladle is in the required spot to enable the charge to be tipped
into the runner which takes it to the converter, the loose wrought-iron
handle, A, is slipped on to the square end of the wormshaft, and by
turning this the ladle is tipped, and at the same time travels on the
rack from its position in the center of the carriage, one man being
sufficient to perform the operation. The dotted lines at B represent a
wrought-iron shield for protecting the tipping gear from splashes of
metal, etc.

[Illustration: IMPROVED LADLE CARRIAGE.]

With the old cast-iron frame carriage the weight of the ladle and
charge is practically carried by the two bearings on one side, as the
ladle has to be overhung from the center of the carriage, in order that
the metal may tip clear of the rails and into the well; supposing of
course there are not conveniences for tipping direct into the converter.

It will be seen that in Mr. Wood's arrangement, when the ladle is in a
vertical position it stands fairly in the middle of the carriage, but
the action of tipping carries it to the side, so that the charge will
clear the rails. This carriage has now been in work for about three
years, and since its introduction there has not been the slightest
hitch, even when running ten tons of metal at a considerable speed
over the six miles of line from the Sirhowy furnaces. This has been a
pleasing contrast compared to the trouble that used to be experienced
at Ebbw Vale with the original cast-iron frames. These, under the heavy
duty put upon them, were continually breaking on the side which had to
carry the weight, and this would entail the metal having to be tipped
on the ground so that it might be broken for recharging.

Although the exceptional nature of the work at Ebbw Vale called forth
this arrangement, it will of course be understood that the advantages
it possesses are also manifest upon shorter journeys.--_Engineering_.




THE REPAIR OF BOILER TUBES.[10]


[10] Annales Industrielles.

The tubes of tubular boilers must, for different reasons, be taken out
when the generator has worked for a certain length of time. Such a
necessity presents itself when the extremities of the tubes are worn
out and can no longer be fastened with sufficient tightness into the
plate, or when the portion of the tube in contact with water is so
incrusted that there results a notable diminution in the production of
steam, or when the tubes exhibit local injuries, or, finally, when the
interior of the boiler must be examined.

[Illustration: REPAIR OF BOILER TUBES.]

This latter contingency arises for every boiler after a period of
from 6 to 8 years, and it requires the removal of all the tubes. It
furnishes an occasion to remedy the other defects, that would have of
themselves required the renewal of only a certain number of the tubes.
In the interval between these thorough inspections defects may present
themselves which require the removal of a certain number of tubes. The
frequency of such repairs depends upon the nature of the feed water,
upon the quality of the fuel, upon the pressure at which the generator
operates, upon the state of repair in which the boiler is kept, and
naturally also upon the quality of the metal of which the tubes
themselves are composed.

Selenitic water deposits in the long run a very hard and adhesive
incrustation, which acts as an obstacle to the transmission of heat.

The more calcareous waters fill the intervals between the tubes with
deposits which can be but partially removed by the washing of the
boiler, and which often form a calcareous mass such as to prevent all
circulation of water around the tubes.

In both cases the tubes are heated beyond measure, elongate, detach
themselves from the tube-plates, and burn in places, or lose enough of
their resistance to allow them to become flattened by the pressure of
the steam.

The loosening of the tubes likewise acts injuriously upon the plates,
which the pressure causes to bend outwardly. The result is that the
tubes may become completely detached.

Sulphurous fuel corrodes the extremities of the tubes near the fire-box
and also notably attacks the hind extremities, in the interior, against
the tube-plate. It likewise renders brittle those tubes whose metal is
bad, so that they split either of themselves or at the least effort
made to tighten them up in the tube-plate.

In tubes made of poor metal these brittle places are not only found
near the plates, but also in other parts.

The tubes likewise have to undergo too lively a combustion when the
boilers are driven. Leakages from the tubes often proceed from the fact
that an expansion of the boiler lengthwise is prevented, or from a
cooling of the tubes by a current of air which passes, without becoming
heated, through a badly covered grate. Leakages may also occur if a
boiler that has just been emptied is filled too soon.

It will be seen that the causes of the deterioration of tubes are
numerous; and the repairs that they give rise to in railway shops are
therefore very important, and are generally known as a whole. Yet they
differ in some points of detail according to the shop in which they are
made, so that it may not be without utility to pass them in review,
in order to compare the results of the practice of several persons
pursuing the same object.

The author of this article has had, during a long experience, occasion
to make such comparisons: several of the methods that he describes were
derived by him in shops that he directed, and have been applied upon a
large scale; and numerous visits to other shops have permitted him to
see different processes and to judge of results.

The different repairs to be made in boiler tubes may be classified as
follows:

1. Repairs to leaky tubes.

2. Removal of worn-out tubes.

3. Repair of tubes in service, and putting them in place again.


1. REPAIR OF LEAKY TUBES.

Leakages at the point of insertion of the tubes are still generally
and exclusively repaired by means of roller apparatus for opening the
tubes, and with which an endeavor is made to tighten the latter in the
hole in the tube-plate.

The cones which were formerly employed injured the ends of the tubes by
splitting them; if the workman was not very skillful, the holes in the
plate became oval; and fractures likewise quite often occurred between
the holes in the plate itself.

The best apparatus to open the tubes are those in which the wedge that
separates the rollers is actuated by a screw; those in which the wedge
is driven in by a hammer are scarcely better than the old cones.

When apparatus for opening tubes are used, care must be taken to
begin with the external tubes, and to open these gradually. The
same operation is afterward performed upon the neighboring ones, in
approaching the center, and then the first ones are taken up. The
tubes should never be opened at one operation, but each one should be
subjected to several passes.

At the second pass, the rollers should be placed a little more deeply,
and should then be half within the tube-plate. The tube thus opens
behind the plate and forms a bearing against it, and this not only
renders it tighter, but also increases its adhesion to the plate.
Finally, the operation is finished by beating down the edge of the tube
that has been raised a little by the preceding pass. If this edge is
already somewhat deteriorated, or if it is not very thick, tightness
may be had by means of rings. The use of rings should be avoided as
much as possible, because they diminish the section of the tubes, and
render the cleaning of their interior more difficult. They should only
be employed as an exception, and should be considered as an unavoidable
evil. Even in old boilers, in which the holes have become oval, they
should be considered only as a means of rendering a small number of
tubes tight.


2. REMOVAL OF WORN-OUT TUBES.

The tubes are taken out independently of one another through the front
tube-plate, after an incision has been made with a chisel through the
part of the tube that is fixed into the back plate. When the holes in
the front tube-plate are not greater in diameter than the external
diameter of the tube, and the latter is incrusted, this process becomes
very difficult, and the use of it often completely spoils the tube. In
fact, we can only remove the tube by live force, and for this purpose
we either use the shock of a heavy body or mechanical apparatus upon
whose arrangement I shall not dwell.

In all cases the holes of the tube-plate are injured. The edge of
these must, in fact, detach the scale from the tube before the latter
can be removed from the boiler, and, when a little of this scale
remains adherent, it produces grooves in the hole, which render it
very difficult later on to make the new tube tight. It is consequently
preferable to cut the tubes immediately back of the plates by means of
a special apparatus consisting of a cone provided with a small circular
steel saw.

This operation should be begun at the bottom of the boiler near the
blow-off plug, and be continued in advancing toward the top. The cut
tubes fall to the bottom of the boiler, and are removed through the
blow-off hole of the front tube-plate. The pieces of tube that remain
in the plate are afterward easily removed by cutting them with a chisel.

If there are but few tubes to be removed, a passage is made for them
toward the blow-off plug by removing a few of the tubes beneath. When
the tubes to be removed are not too far from the plug, this method is
very satisfactory. Even though there were a few more tubes removed, the
cost of such removal would be more than compensated for, because this
method is cheaper, and preserves the tubes and plates, and because the
boiler, by receiving a larger number of clean tubes, will afterward
utilize the fuel better.


3. REPAIR OF TUBES IN SERVICE, AND PUTTING THEM IN PLACE AGAIN.

Either when the removed tubes are to be employed anew, or when they
are to be classed as old material, it is equally necessary to free
them from the incrustation that covers them. The methods employed vary
according to the shop.

The cleaning of tubes by beating or scraping the incrustation is
very difficult, and requires much time. In some shops the tubes are
dipped into an acid bath. In this way only the incrustation composed
of carbonate of lime is dissolved, that into the composition of which
sulphuric acid enters not being attacked.

In some large shops there are iron drums in which the tubes are placed.
When these drums are revolved the incrustation becomes partially
detached, but very rarely completely, and it is always necessary to
finish the work by hand. It also happens that the bits of scale that
become detached and that remain between the tubes produce grooves
therein; besides, the cost of installing these drums is quite high.

Per contra, the writer has seen a, as yet, little known method employed
in the shops of the Berlin-Hamburg Railway, one that he has used
himself, that he has introduced into several shops, and that he can
recommend as the best. The tube to be cleaned is submitted to a rotary
motion around its longitudinal axis. The workman grasps it with a sort
of wooden pincers whose jaws are provided with coarsely toothed steel
plates, and, pressing the legs of this more or less tightly, slides it
slowly along the tube. The incrustation is thus reduced to dust, and
the tube, after the operation, is absolutely clean.

The apparatus used for revolving the tubes is shown in Figs. 1 to 3. It
consists of quite a short shaft, which revolves in two pillow-blocks
and receives its motion through pulleys. Outside of the bearing to the
right, this shaft terminates in a cone provided with channels whose
diameter is proportioned to that of the tubes.

The tube to be cleaned is firmly fixed upon the cone, and provided
at its other extremity with a plug that serves to center it. As the
cleaning is accompanied with much dust, it must be done in open air or
in a special shop.

At the same time, a classification is made of the damaged tubes
that can no longer be employed, except as ends of the tubes that
may be employed in shorter boilers, and of those that are entirely
unserviceable.

Every time a tube is removed it loses 70 to 80 mm. of its length in
the two cuttings. When we have locomotives that are provided with
shorter boilers, we have a direct use for the removed tubes, but if the
contrary is the case the tubes must be lengthened. Such elongation is
effected in three ways, viz., by drawing them out, by soldering copper
ends to them, and by uniting iron ends to them with a hammer.--_F. W.
Eichholz, in Organ fur die Fortschritte des Eisenbahnwesens._




GRULET'S SCREW FOR RAISING WATER.


The French Agricultural Machinery Company has recently made a very
interesting application of the screw for raising water for submersion
and irrigation, and, to our knowledge, it is the first of its kind.

It is only necessary to examine the accompanying cut and observe the
dimensions of the machine (which was constructed according to plans of
Mr. Grulet) to recognize the fact that we have here a really practical
application.

The screw, which constitutes the principal peculiarity of the system,
has six blades, with a pitch of 0.465 m. On making 210 revolutions
per minute it is capable of raising about 435 liters (95 gallons) per
second to a height of 1.2 m (about 4 feet). The shaft that drives it
revolves in a bearing which is bolted to a cross piece that is affixed
to the cylindrical chamber. This latter consists of a cast iron case
that is easily taken apart, and of a strong cylinder of iron plate
whose upper extremity is connected, by means of riveted angle iron,
with the bottom of the sluice. In the interior of the cylinder there
are two cones, whose bases embrace the hub of the screw in such a way
as to obtain a continuous superposition of the layers of liquid, and
prevent bodies in suspension from penetrating between the rubbing
surfaces of the bearing. One of the cones is made of iron plate, and
is connected with the principal cylinder by four radiating braces and
small angle irons, and the other is cast in a single piece with the box
of the pivot.

The rotary axis is guided above by two pillow blocks held by the cross
pieces of a frame that is riveted to the sides of the sluice. Finally,
this latter terminates in a hinged gate which regulates the flow of the
water.

Two beams that rest upon the sides of a stream will suffice in most
cases to support the entire affair.

The mechanical duty of the apparatus is estimated at about 65 per cent.
In the apparatus put up by Mr. Grulet, the motive power is furnished
by a portable 10 H.P. engine. The boiler is a return flame one, with
movable fire place, and the steam cylinder has a diameter of 0.2 m. (8
inches) for a piston stroke of 0.3 m. (about 12 inches). Before the
apparatus was finally put in place it was sent to the last exhibition
at Carcassonne, where it attracted very much attention from visitors.
Its great regularity in working was particularly remarked. This
quality, and the simplicity of its construction and the ease with which
it may be put in place, are valuable features in apparatus that are
designed to be looked after by inexperienced persons, and to operate in
open air far from repair shops.--_Revue Industrielle_.

[Illustration: GRULET'S SCREW FOR RAISING WATER.]




ON VARIOUS TONING BATHS.[11]

By W. M. ASHMAN.


[11] A communication to the London and Provincial Photographic
Association.

In alkaline toning with borax or acetate of soda, the first
consideration is to free the paper as much as possible from the excess
of silver nitrate remaining therein over and above the quantity used
in the production of the print; this is termed washing away the free
silver. That operation is satisfactorily performed by soaking the
prints in a few changes of clean soft water, usually four, or until the
water is no longer opalescent when tested with a few grains of salt.
The washing water so obtained is collected in the manner described to
you by Mr. F. W. Hart, and precipitated with dilute hydrochloric acid.
The vessel employed should be scrupulously clean, either earthenware,
porcelain, or wood answering the purpose.

_Experiment_ 1.--The treatment of the prints is sometimes followed
by passing them into a dilute solution of sodium acetate or ordinary
common salt, about one per cent., such as here shown, and stirring
them about for five minutes, when it will be seen they have assumed a
brick-red color, the object of which is threefold: First, the fibers
become charged with a substance which acts as a chlorine absorbent, a
necessary property to be mentioned further on. Secondly, a definite
color is insured to start with, thus obviating the possibility of
mistaking fresh prints in the toning bath for those which have become
purple by reason of the deposited gold, an important consideration when
dealing with fumed paper. Thirdly, the last trace of free nitrate of
silver is removed, thereby preventing a too rapid decomposition of the
toning bath.

Theoretically considered, it is proper that the last trace of silver
nitrate should be removed; but those who are engaged in the daily
practice of commercial work do not insist upon the strict observance
of such a rule in all cases. An especial exception is permitted and
advocated when dealing with prints from weak or underexposed negatives,
this class being found to yield richer tones by not washing any of the
free silver out.

The plan of soaking prints in a solution of sodium acetate was
originally recommended, in lieu of washing, by a member of this
Association, Mr. A. L. Henderson, as long ago as 1861, the following
being an outline of the method suggested by him: Slightly overprinted
proofs were soaked in a bath composed of

  Sodium acetate                       240 grains.
  Water                                 10 ounces.

The unwashed proofs were moved about in this solution at least ten
minutes, in order to convert all the free silver nitrate into acetate
of silver. After slight rinsing in clean water the proofs were toned
with

  Gold terchloride                       4 grains.
  Sodium acetate                       240   "
  Water                                 10 ounces.

Among the advantages claimed was an entire absence from mealiness, a
defect, you will remember, we now avoid by the adoption of ammoniacal
fuming.

Guide-books to the practice of printing usually recommended three
rapid washings; the decomposing action thus set up by the quantity of
free silver remaining in the paper materially quickens the speed of
toning. To prevent a too rapid deposition of gold some printers prefer
adding a small quantity of common salt to the toning bath, which turns
the prints sufficiently red and acts in some respects equal to an
intermediary bath.

Preserved papers--containing, as they generally do, a certain
proportion of free acid--are liable to give some trouble in toning,
owing to the retarding action of the acid present. When this occurs, it
is in a great measure overcome by the use of an intermediate bath of
an alkaline character and sufficient strength to neutralize the acid.
Either the carbonates of ammonia or soda are found useful for this
purpose, and I cannot do better than quote the one mentioned by Mr.
Frederick York, which, it will be remembered, is composed of

  Washing soda                         1 ounce.
  Water                                1 gallon.

Prints treated in the manner described are ready for toning by the
alkaline method to be dealt with later on.

This brings us to the consideration of toning baths generally. The
properties of toning baths vary somewhat according to the mode of
preparation. The term "toning," as we understand it, implies a
certain change of color brought about by chemical means, such as the
deposition of a stable metal upon one that is easily affected by the
atmosphere--electrolysis, in fact.

Evidently Mr. W. H. Fox Talbot was the first to use the toning bath
in connection with paper photography, although he does not seem to
have made much headway with his process at first; for it is recorded
that from January, 1839, the date when Mr. Talbot communicated his
discovery to the Royal Society, until 1845 very little improvement took
place. These early paper pictures, be it remembered, were designated
"photogenic drawings." Talbotype was not patented for some time
afterward.

In the year 1845, however, it was found that steeping the paper in
terchloride of gold vastly improved the results. It was not until 1853
that albumen took any part in the production of prints, the honor of
its introduction being ascribed to Mr. Henry Pollock, although it seems
that M. Le Gray, of Paris, about that time was producing stereoscopic
pictures on albumenized paper. To M. Le Gray is due the credit of
introducing gold toning in lieu of sulphur. The first toning then was
performed by the decomposition of hypo., and known as "sulphur toning,"
by which fine black tones were obtained upon the addition of an acid,
such as acetic, sulphuric, or other suitable oxidizing substance to the
hypo., gold taking no part in this process. Unfortunately, prints so
treated are said to be the least permanent of any; but of that I can
bring no actual proof, never having employed the process.

_Experiment 2.--Toning by Sulphur._--We have an unwashed silver print
here in a twenty per cent. solution of hypo., and to that we now add
a few drops of slightly dilute sulphuric acid. It will be seen that
a straw-colored substance is immediately liberated, which is sulphur
in an exceedingly fine state of division, and this becomes attached
to the print. Toning action goes on, through the silver image being
tarnished, or, more correctly, converted into sulphide of silver. This
liberation of sulphur may be expressed by the following equation:

  Hypo.              Sulphuric Acid
  Na_{2}S_{2}O_{3} + H_{2}SO_{4}   =

  Glauber Salts    Water     Sulphur Dioxide     Sulphur.
  Na_{2}SO_{4}   + H_{2}O  + SO_{2}             + S.

With respect to the reaction which takes place when toning a silver
image with sulphur, I will quote a few lines from the parent work
of reference for nearly all recent writers, namely, Hardwich's
_Photographic Chemistry_, wherein we find the following paragraph:

"It is well known that articles of silver plate become darkened by
exposure to the fumes of sulphur, or to those of sulphureted hydrogen,
of which minute traces are always present in the atmosphere. If the
stopper of a bottle of sulphureted hydrogen water be removed, and a
simply-fixed photographic positive suspended over it, the picture will
lose its characteristic red tone, and become nearly black. The black
color is even more intense than an experienced chemist would have
anticipated, because analysis teaches us that the actual quantity of
silver present in a photographic picture on paper is infinitesimally
small; and it is well known that sulphide of silver, although of a
deep brown color, approaching to black when in mass, exhibits a pale
yellow tint in thin layers, so that a mere film of silver converted
into sulphide possesses very little depth of color. To explain the
difficulty it has been suggested that the toning action of sulphur
on a red print is probably due to the production of a sub-sulphide
possessing an intense colorific power, like the sub-oxide and
sub-chloride of silver. When the toned picture is subjected to the
further action of sulphur, is converted into the ordinary protosulphide
of silver, and becomes yellow and faded."

The toning baths following the sulphur method were principally mixtures
of gold terchloride and hypo. This latter substance was found to be a
solvent of certain silver compounds by the Rev. J. B. Reade, in 1839,
Mr. Talbot having previously fixed his prints with common salt. Prints,
too, were fixed first in some cases, and toned afterward, washing
away the free silver being more or less practiced in the mixed hypo.
and gold and the sulphur toning processes. When fixing was employed
before toning, it was usual to soak washed prints in a twenty per cent.
solution of hypo. for a period of ten minutes, or until the soluble
silver salts were removed, the resulting color being a disagreeable
yellowish-brown. To improve the result so obtained the prints were
passed into a solution of--

  Gold terchloride                     10 grains.
  Water                                20 ounces.

When toning action quickly followed, the yellow color giving place to
that of a dark sepia tint. From this stage to that of mixing these
two substances together was only a natural sequence, and effected a
diminution of gold to the extent of one-fourth, as will be seen by the
following recognized formula:

  Hypo.                                 7 ounces.
  Water                                20   "

When dissolved, add--

  Gold terchloride                      5 grains.
  Dissolved in water                   20 ounces.

After mixing, a clear solution should result.

The _sel d'or_ process followed, and was expected to give still better
results. It was found, however, that the solutions would not keep;
and as a considerable quantity of the gold salt was needed, it caused
experimenters to search for a less expensive method. One decided point
in its favor was the circumstance that prints suffered no loss of
intensity during the operation, as they do in the case of all other
toning methods. Briefly: the prints were well washed to extract free
silver, and, after soaking five minutes in salt and water, they were
passed into an alkaline solution composed of--

  Liquid ammonia                        60 minims.
  Water                                 20 ounces.

Here they became very red. After washing in clean water the surface was
flooded with a toning solution composed of

  Double hyposulphite of gold and sodium (_sel d'or_)  1/2 grain.
  Hypo                                                 1   "
  Water                                                1 ounce.

Upon the print assuming a purple-gray color it was withdrawn and fixed
in a sixteen per cent. solution of hypo. to dissolve the unacted upon
silver chloride. Gold, when in a fine state of subdivision, is of a
rich purple color. The layer obtained by deposition upon a silver image
is very finely divided; hence the color. The only object in continuing
the toning action beyond the stage at which a good surface color has
been reached is to obtain a deposit of sufficient density to completely
neutralize the red color of the organic silver image beneath;
therefore, it is preferable, in forming a judgment of toning action, to
examine proofs by transmitted light rather than by reflected only.

Before dealing with the various formulae for alkaline toning I should
like to step out of the golden track to say a few words on platinum
tetracloride, PtCl_{4}.

_Experiment_ 3.--_Platinum Toning._--The value of a platinum salt as a
toning agent for silver images has been thoroughly demonstrated before
you by Mr. Henderson, when he initiated us into the secrets of ceramic
photography. My trials with this salt as a toning agent for paper
proofs have only been partially successful. By that I mean that toning
does take place when a dilute solution is employed, but the action is
too tardy for demonstration here to-night, since anything like a black
tone could not be obtained under half an hour. You will observe that
the surface becomes covered with chloride, showing the necessity for
copious washing. Yellow or discolored prints are bleached when toned
in this bath, the whites becoming very pure. The formula here given
is capable of producing a very good shade of brown in less time, and
should be permanent, since platinum is a metal practically unaffected
by the atmosphere; and I think there is good reason to suppose that
if a thin coating of platinum could be deposited on the silver image,
the protection offered would be more economical as well as stable.
Something has already been done in this direction, but not in recent
years.

The following is the composition we are now using:

  Platinum tetrachloride, sirupy solution,
    color of old East India sherry        5 minims.
  Hydrochloric acid                     150   "
  Water                                  20 ounces.

Wash away the free silver thoroughly, warm the toning solution to 70 deg.
Fahr., and fix in a twenty per cent. hypo. bath.

Mr. A. Watt, in the second volume of the _News_, gives a formula which
runs as follows:

  Solution of platinum                   30 minims.
  Hypo.                                   3 grains.
  Hydrochloric acid                       5 minims.
  Water                                   5 ounces.

This bath is said to act instantly, but I have not had an opportunity
to test it. The strength of the platinum solution here given is
indefinite, but any of our experimental members can soon ascertain the
amount of dilution necessary to obtain the most favorable results.

_Alkaline Toning._--Owing to the bleaching action which occurs in
toning silver prints with gold, which is slightly acid, certain
experiments were made, and it was found that bleaching increased in
proportion to the quantity of hydrochloric acid added. Now, in the
action of toning chlorine is disengaged, and in order to render this
powerful bleaching agent inert it has been proposed to introduce a
substance capable of combining with it, and thus, in absorbing it,
prevent undue loss of vigor. To obtain this a slightly alkaline toning
bath became a necessity, and to Mr. Waterhouse we are indebted for the
introduction of the alkaline salts (Hardwich).

Here is an example:

    _Experiment_ 4.

  Sodium carbonate (Na_{2}HCO_{3})        5 grains.
  Auric terchloride (AuCl_{3})            1 grain.
  Water                                  10 ounces.

Instead of the dry bicarbonate we will use a saturated solution. In
this as well as the following experiments we shall tone three prints of
the same subject, viz., ordinary, fumed, and preserved.

Mr. Maxwell Lyte has written on and investigated the properties of
toning solutions a great deal more than most men, and we find the
following emanating from Mr. Lyte:

  Sesquichloride of gold                 15 grains.
  Phosphate of soda                     300   "
  Distilled water                         1-3/4 pints.

And in the same communication it is mentioned that 180 grains of borax
may be substituted for the phosphate with a like result. Therefore
it will be seen that a borax toning bath is not of recent discovery,
although it does not appear to have been quoted in many formulae for at
least a dozen years after its publication.

After the publication of Mr. Lyte's formulae it was found that other
salts behaved similarly; and among the first suggested we found sodium
acetate, the qualities of which, extolled by the introducer, Mr.
Hannaford, have since been verified by the whole photographic world.
Here is one of the ordinary formulae:

    _Experiment_ 5.

  Gold terchloride                        1 grain.
  Sodium acetate                         10   "
    "    chloride                        10   "
  Hot water                              20 ounces.

Mix twenty-four hours before use. Neutralize with chalk or whitening
(carbonate of lime).

The name of M. Le Gray must be mentioned as the originator of the lime
and gold toning bath; although the original formulae differ somewhat
from the one now used, the results are identical. The original formulae
consisted first in washing away a portion of the free silver by soaking
the proofs for a few minutes in two changes of water, then submitting
them to the action of an auriferous bath, composed of

  Terchloride of gold, 1 per cent. solution           1 part.
  Hyperchloride of lime (white powder)                3   "
  Distilled water                                 1,000   "

The action was complete in ten to fifteen minutes, when the prints
required washing in two changes of water to free them from the chloride
of lime remaining in the fibers previous to fixing in one to six of
hypo. If the tone were satisfactory at the expiration of fifteen
minutes, the ordinary washing could be proceeded with; if not, the
proofs were submitted to a final bath composed of:

  Gold terchloride                                    2 parts.
  Hypo.                                             200   "
  Distilled water                                 1,200   "

M. Le Gray says: "The proof ought not to be left in this bath less than
fifteen minutes, as that is the minimum time necessary to insure the
permanency of the picture; but it may be allowed to remain in it for as
much longer as is requisite for obtaining the desired tone." Efficient
washing in warm and cold waters completed the operation. Should any of
our provincial members experience a difficulty in obtaining calcium
chloride for their experiments, it can be easily made by causing dilute
7 to 3 hydrochloric acid to react on common whitening, and when neutral
filter and set aside for the crystals to separate out.

_Experiment_ 6.--The uranium and gold toning bath has many friends. The
tones are said to be richer and to economize gold, while it is very
easy to work. I am unable to give the author's name, but I can present
a formula which has worked well in my hands. After washing away the
free silver tone in the following mixture:

    No. 1.

  One grain acid solution of gold terchloride    1 ounce.
  Water                                          7 ounces.

Neutralize with sufficient of a twenty per cent. solution of sodium
carb. (Na_{2}HCO_{3}).

    No. 2.

  Three grain solution of uranium nitrate         1 ounce.
  Water                                           7 ounces.

Neutralize as in No. 1. Warm each to 70 deg. Fahr., and mix. The bath is
then ready for use. It can be used repeatedly if desired by acidifying
with citric acid and neutralizing before use; but nothing is gained by
using it a second time.

There are methods of toning which resemble more or less those which
have occupied our attention to-night; among them may be mentioned the
tungstate bath, likewise citrate of soda. The vermilion bath, too,
might afford sufficient matter alone for a lecturette. If some one
experienced with it could be induced to bring it before us, I am sure
it would prove interesting.




COATING PLATES WITH GELATINE EMULSION.


To coat plates perfectly, says H. S. Starnes in _British Jour. of
Photography_, I found the following points were necessary:

1. That a certain quantity of emulsion should be flowed in one even
stream all over the plate, instead of pouring the emulsion in a pool in
the center of the plate and then dispersing it over the whole surface;
because in the latter mode of coating large plates the gelatine is apt
to commence setting before it is equally distributed, and an unequally
coated plate is the result.

2. The plate ought to be put on the leveling-table before coating, and
not be moved before the gelatine is set; because in the dull light of
the dark room it is so difficult to prevent the emulsion running off
the plate when putting it down on the leveling-table.

3. I found that if the emulsion be rubbed (so to speak) on to the glass
there is much less chance of frilling, etc., than if it were poured
on. I think it is because in the former case the gelatine is in firmer
contact with the glass. When the gelatine is poured on to the plate
the cold glass instantly chills it, and by the time the emulsion has
reached the edges of the plate it has so far set as to have partially
lost its power of adhesion to the smooth surface of the glass.

[Illustration: Fig. 1.--Showing melted emulsion in coater ready for
coating.]

Two or three years ago, when it was the practice to warm the plates
before coating, I found from a series of experiments I then made that
when a plate was warmed before being coated the emulsion commenced
setting on the surface of the film, and of course in setting
contracted, thereby leaving a partial vacuum between the film and the
glass. On development frilling was the consequence. I found, however,
that, when pouring the same emulsion on cold glass, on the portion
of the plate where it was poured on, the film instantly chilled and
commenced to contract on to the glass, and it never frilled there; but
toward the edges of the plate, as the emulsion had commenced to chill
before they were covered, the film was not in such perfect contact with
the glass. Any person can try the experiment by first coating a plate
in the ordinary way, and on the second plate just pour a small pool
of emulsion on the center; let both dry, and he will then see after
exposure which frills the easier on development.

[Illustration: Fig. 2.--Showing emulsion flowing through the slit on to
the glass.]

After a series of experiments I found that by brushing a substratum of
emulsion on to the cold plate (with a brush made by binding a strip
of wash-leather at the end of a strip of glass), and then pouring the
full quantity of emulsion on to the substratum (for quarter-plates I
used a small silver teaspoon, which held sufficient to cover that size
of plate), I found I could coat plates far better and quicker and as
easily as when coating with collodion, and I got over the difficulties
of having frilling plates.

When only a few small plates are required--such as for experimental
purposes--I believe this method is as quick and good as any; but when
several dozen plates are wanted, any plan of coating them separately
takes a long time. With my plate-coater I can coat a dozen plates in
about the time I formerly took to coat one. When coating a number, I
thought it would be best to lay them in rows on the leveling-shelves
and draw the receptacle containing the emulsion over them, rather than
keep the latter a fixture and run the plates under it either on an
endless band or sliding shelves; because by the first mode the plates
can be fixed close together, and the emulsion is less likely to get
between them.

The coater is a species of wooden tray (of which the diagrams show the
section), having a small slit in one of the bottom edges through which
the emulsion passes in one even wave the whole width of the plate. The
width of the coater is the same as that of the plate, though one six
and a half inches wide can be used for either half or whole plates.

[Illustration: Fig. 3.]

I find the best way of making it, so as to get the slit an equal
opening the whole length of it, is to put the back, bottom, and two
sides together first, as in Fig. 3. Then by putting a piece of very
thin paper (A B) on the angle piece when the front piece of wood is put
tight down on the paper and fixed in its place, and the paper is drawn
out, it will be found that the slit is very even. In one coater I made
I had the slit a little too wide an opening, and to reduce it I glued
a piece of muslin over it. This I found was a great improvement, as it
not only acted as a strainer, but it checked and caused a more even
flow of the emulsion over the plate. I varnished the wood and muslin
(except over the slit) with black Japan.

To coat the plates I put them close together in rows on the
leveling-shelf, as shown below:

[Illustration: Fig. 4.]

A is a thin, narrow ledge of wood. B B B are thin pieces of wood, in
the center of each of which is a small slot and thumb-screw. The plates
are pressed against A by the pieces of wood, B, and the thumb-screws
are then fastened. The plates are thus kept from slipping about. All
this, of course, can be done in ordinary white light. The light is then
made non-actinic; the melted emulsion is poured into the reservoir of
the coater, which is put to the left hand edge of the outer row of
plates. It is then lifted up on edge, as in Fig. 2, and drawn slowly
over the row of plates, and so on until the whole of the rows are
coated. Of course when not coating plates it is kept in a horizontal
position, as in Fig 1. The emulsion on the plates is allowed to set
without being disturbed; the shelf is then slipped into the drying-box
until the plates are dry, so that they are not touched from the time
they are coated until they are dry and ready for packing.

I am at present engaged in making a modification of this coater to hold
a much larger quantity of emulsion at one time, when a large number of
plates require to be coated. It is something the shape of a flat teapot.

[Illustration: Fig. 5.--A A is a piece of curved glass. B a piece of
coarse ground flat glass, ground side uppermost, sliding in two grooves
in the wooden side. C is the handle fixed to the wooden back.]

A piece of thin paper is placed on the curved glass, and the ground
glass pushed close up and fixed by two small wedges, D. The paper
is then slipped out, leaving a narrow, even opening between the two
glasses. The width of this opening can be varied by using thicker paper
if the plates require to be coated with a thicker film. By using this
form the coater can be more easily cleaned, as the ground glass can be
slipped right out at the back, and probably in passing from the opening
to the plates over the curved glass the wave of the emulsion will be
equalized as well as when passing through the muslin.




IODO-CHLORIDE OF SILVER EMULSION.

By V. SCHUMANN.


In a recent paper in the _Wochenblatt_, says the _Photographic
News_, this investigator relates his experience of gelatine emulsion
containing chloride and iodide of silver. Gelatine films containing
pure chloride of silver can only be used in the camera in exceptional
cases; if, however, iodide be added, the resulting iodo-chloride
films answer most of the purposes of a gelatino-bromide plate. It may
be remarked that with gelatino-chloride emulsion an image is easily
developed with pyro or oxalate; but unfortunately, fogging is very
liable to set in. On strongly diluting the developing solution and
adding a large proportion of bromide, it is possible to obtain a
clear deposit, but the image is so thin that it is quite useless for
practical purposes.

Gelatino-iodide films possess totally different properties. The
development is extremely slow, without any tendency to fog; thus the
addition of a restrainer should be avoided. Iodo-chloride emulsion can
be prepared either by dissolving the chloride and iodide salts in the
gelatine solution, and then adding by degrees the silver nitrate; or
by making two separate emulsions of chloride and iodide of silver, and
then mixing the two after the washing process. It should be noted that
the properties of a compound or a mixture of the two haloids are very
different. A negative of the spectrum impressed on an iodo-chloride
film, prepared by mixing the two emulsions, shows two colored deposits.
The red end of the spectrum as far as the G line is reproduced in
the negative as a red tone, while that part of the spectrum from G
extending to the violet appears as a grayish violet deposit. When using
Stolze's potash developer, the difference of the two tones on the
negative appears even more marked.

Experiments were instituted to determine the most suitable proportion
of the silver haloids to be suspended in the emulsion. For this purpose
three emulsions were prepared according to the following formulae:

  No. 1.--IODO-CHLORIDE EMULSION.

  A.--Ammonium chloride       0.64 gramme.
      Potassium iodide        0.05 "
      Gelatine                1.5 "
      Water                   15 c. c.
  B.--Silver nitrate          1.55 gramme.
      Water                   15 c. c.

No. 2.--Same as No. 1. but with 0.15 potassium iodide instead of 0.05;
and 1.65 silver nitrate instead of 1.55.

No. 3.--Same as No. 1, but with 0.64 potassium iodide instead of 0.05;
and 2.14 silver nitrate instead of 1.55.

To prepare the emulsion, A and B were heated in a water bath and then
mixed slowly, with thorough shaking. The mixture, after an hour's
cooking, was allowed to stand over night; the emulsion was next washed
for seventy-two hours, and after slightly diluting, at once poured
over the plates. The emulsions prepared according to formulae 1 and
2 transmit blue light, which, however, is much brighter than that
exhibited by gelatino-bromide emulsion. No. 3 emulsion transmits an
orange light.

Previous to cooking the emulsion, a small quantity from each sample
was spread on a glass plate, and, with the films prepared from the
fully digested emulsion, were placed in sunlight. The unripe emulsion
darkened much more quickly than that which had been digested. The
colors of the exposed films prepared according to Nos. 1 and 2 were
chocolate, and there was very little difference between the tones of
the ripe and unripe emulsion. With the plates made by No. 3 formula
there was, however, a great difference of color noticeable; thus, while
the unripe emulsion yielded a deposit not unlike that of Nos. 1 and
2, the films prepared from the ripe emulsion assumed a grayish green
color, which did not alter even after some weeks' exposure to daylight.




APPARATUS FOR SATURATING WATER WITH SULPHUROUS ACID.


Messrs. A. Boake & Co., of Stratford, London, England, have devised
a convenient apparatus for charging water with sulphurous acid which
is useful in the making of photographic developers. The following
description has been furnished by the firm:

The figure shows one of the siphons connected with a very convenient
form of apparatus for preparing a solution of sulphurous acid in water,
or of sulphites, as may be required.

The siphons are easy to manage, the flow of gaseous acid being
regulated with the greatest nicety by simply turning the milled head
shown in the engraving, the liquid acid being gradually converted
into gas as the pressure is relieved. There is, moreover, no danger
attending the use of this simple apparatus; sulphurous acid exerting at
ordinary temperatures a pressure of about 30 pounds on the square inch,
while each siphon is carefully tested under a pressure of 200 pounds on
the square inch before being sent out.

[Illustration: APPARATUS FOR SATURATING WATER WITH SULPHUROUS ACID.]

In preparing a solution, say, of sulphurous acid in water, the ground
stopper carrying the tubes for passing the gas should be removed from
the glass jar in immediate connection with the siphon, and two-thirds
filled with distilled water; the stopper is then to be replaced, and
the second glass jar half filled with caustic soda solution. The soda
solution is used to absorb any sulphurous acid not dissolved by the
distilled water, and so prevent the escape of this irritating gas into
the air. Solution of sulphite of soda, and also of bisulphite, can be
prepared in a similar way, substituting only pure caustic soda solution
for the distilled water employed in the case of preparing the solution
of sulphurous acid; but we must rather devise the purchase of the pure
solid forms of these salts specially prepared, and put up by us in
one-pound stoppered bottles for use in photography; these preparations
can be obtained either direct from the manufacturers or from any
wholesale chemical firm. The siphons may be obtained either separately
or already connected with the absorbing jars. It may be mentioned
that these siphons contain about two and a half pounds of liquefied
sulphurous acid, and can be refilled when required; but those requiring
larger quantities can obtain the acid compound in copper drums.

_The Photographic News_ says: It will be noticed that Messrs. Boake
say there is no danger attending the use of the siphons, as the glass
vessels are tested at a much greater pressure than that ordinarily
exerted by the condensed sulphurous acid; but our readers must remember
that a blow against a hard substance may cause the glass to become
fractured, and that under these circumstances the bursting of a siphon
might cause a serious injury. Still, if proper care is exercised, there
need be no accident; but we would suggest that the condensed acid
should always be kept in the coolest place available, as the pressure
it exerts becomes much greater when the temperature is raised.

The above caution is necessary, as a bare statement that there is no
danger may cause persons to handle the siphons without reasonable care.
The risk is precisely analogous to that attending the use and handling
of bottles containing ordinary aerated waters, only the irritating
nature of the sulphurous acid must be taken into account. Instances
have occurred in which serious injury has resulted from the bursting of
a bottle of soda water; but few, if any, are deterred from the use of
soda water or lemonade on this account.




DETERMINATION OF TANNIN.

By E. JOHANSON.


The precipitation of tannin by a solution of gelatin is effected
more completely and in a better condition for filtration if, besides
ammonium chloride, as proposed by Schulze and Lehmann, there is also
added a small quantity of chromium sulphate or of chrome-alum. The
author proceeds in the same manner as Lehmann, but he adds to 100 c.c.
of the solution containing sal-ammoniac from 5 to 8 drops of a solution
containing 1 part chromium sulphate in 25 parts of water. In order to
ascertain the end of the reaction, he filters small quantities into two
test glasses of equal width, adds to the one a few drops of a solution
of gelatin, observing if the two liquids, when held up against a sheet
of black glazed paper, appear opaque or transparent. As long as a
precipitate is formed, these portions and the washings of the little
filters are poured back to the main quantity. If acetic or tartaric
acid is present, the liquid should be neutralized before proceeding to
the determination. Johanson points out that, though this method gives
good results with the tannin of galls and of oak-bark, an extract
of coffee gives no precipitate with solution of gelatin, so that
caffeo-tannic acid cannot be determined in this manner. This shows that
only quantities of tannin of one and the same kind can be compared with
each other.




THE INCOMPLETE COMBUSTION OF GASES.

By HAROLD B. DIXON, M.A.


[Abstract of a paper read before the Chemistry Section of the British
Association at Montreal.]

The author gave a _resume_ of the work he had done in continuation of
the researches of Bunsen, E. von Meyer, Horstmann, and other chemists,
on the division of oxygen when exploded with excess of hydrogen and
carbonic oxide. The following are the general conclusions arrived at:

1. No alteration _per saltum_ occurs in the ratio of the products
of combustion. The experiments made completely confirm Horstmann's
conclusion; Bunsen's earlier experiments being vitiated by the presence
of aqueous vapor in the eudiometer.

2. A dry mixture of carbonic oxide and oxygen does not explode when
an electric spark is passed through it. The union of carbonic oxide
is effected indirectly by steam. A mere trace of steam renders the
admixture of carbonic oxide and oxygen explosive. The steam undergoes
a series of alternate reductions and oxidations, acting as a "carrier
of oxygen" to the carbonic oxide. With a very small quantity of steam
the oxidation of carbonic oxide takes place slowly; as the quantity of
steam is increased, the rapidity of explosion increases.

3. When a mixture of dry carbonic oxide and hydrogen is exploded with
a quantity of oxygen insufficient for complete combustion, the ratio
of the carbonic acid to the steam formed depends upon the shape of the
vessel and the pressure under which the gases are fired. By continually
increasing the initial pressure, a point is reached where no further
increase in the pressure affects the products of the reaction. At and
above this critical pressure the result was found to be independent of
the length of the column of gases exploded. The larger the quantity of
oxygen used, the lower the "critical pressure" was found to be.

4. When dry mixtures of carbonic oxide and hydrogen in varying
proportions are exploded above their critical pressures with oxygen
insufficient for complete combustion, an equilibrium is established
between two opposite chemical changes represented by the equations:

  (I.) CO + H_{2}O = CO_{2} + H_{2}.
  (II.) CO_{2} + H_{2} = CO + H_{2}O.

At the end of the reaction the product of the carbonic oxide and steam
molecules is equal to the product of the carbonic acid and hydrogen
molecules multiplied by a coefficient of affinity. This result
agrees with Horstmann's conclusion. But Hortsmann considers that the
coefficient varies with the relative mass of oxygen taken.

5. A small difference in the initial temperature at which the gases are
fired makes a considerable difference in the products of the reaction.
This difference is due to the condensation of steam by the sides of the
vessel during the explosion, and its consequent removal from the sphere
of action during the chemical change. When the gases are exploded at an
initial temperature sufficiently high to prevent any condensation of
steam during the progress of the reaction, the coefficient of affinity
is found to be constant whatever the quantity of oxygen used--provided
only the quantity of hydrogen is more than double the quantity of
oxygen.

6. The presence of an inert gas, such as nitrogen, by diminishing the
intensity of the reaction, favors the formation of carbonic acid in
preference to steam. When the hydrogen taken is less than double the
oxygen, the excess of oxygen cannot react with any of the three other
gases present--carbonic oxide, carbonic acid, and steam--but has to
wait until an equal volume of steam is reduced to hydrogen by the
carbonic oxide. The excess of inert oxygen has the same effect as inert
nitrogen in favoring the formation of carbonic acid. The variations
in the coefficient of affinity found by Hortsmann with different
quantities of oxygen are due partly to this cause, but chiefly to the
varying amounts of steam condensed by the cold eudiometer during the
reaction taking place in different experiments.

7. As a general result of these experiments it is shown that, when a
mixture of dry carbonic oxide and hydrogen is exploded with oxygen
insufficient for complete combustion, at a temperature at which no
condensation of steam can take place during the reaction, and at a
temperature greater than the critical pressure, an equilibrium between
two opposite chemical changes is established, which is independent
of the mass of oxygen taken, so long as this quantity is less than
half the hydrogen. Within these limits the law of mass is completely
verified for the gaseous system composed of carbonic oxide, carbonic
acid, hydrogen, and steam at a high temperature.




HERBST'S METHOD OF FILLING.

Demonstrated by DR. G. C. CLUDIUS, Grenoble, France.[12]


[12] Translated from the _Revue Odontologique_, for the _Dental Cosmos_.

At the July meeting of the Odontological Society of France, Dr.
Cludius, from Grenoble, made the following demonstration of a new
method of gold filling, saying:

We feel the necessity of making the operation of filling teeth with
gold easier, if possible, especially in difficult cases, in order to
lessen the fatigue of the operator, as well as to prevent the suffering
of the patient, during hours without interruption, under the ceaseless
blows of the mallet. The remedy has been sought in new forms of
material, like sponge and crystal gold. These have not given any help
in the performance of good operations, but have rather facilitated poor
work. We are not in need of varieties in the forms of gold, but we
ought to try and improve its manipulation, and this has recently been
done in a novel manner by Dr. Herbst, whose rotation method has been
mentioned in the dental journals within only a few months; and yet it
seemed necessary that this great invention, made in Bremen, should take
its way by America to come to us.

In the January meeting of the Odontological Society of New York, Dr.
Boedecker mentioned it for the first time, describing the excellence of
fillings made by Dr. Herbst in less than half the time that any mallet
work would have required, and he expressed his intention of going to
study the method with the inventor. Thinking that I was yet nearer to
Bremen, I went thither, and found there Dr. W. D. Miller, who had come
on the same errand. Mr. Brasseur had also written to Dr. Herbst, and it
is by his (Mr. B.'s) invitation that I came to Paris to show you what
I have learned in Bremen. To-morrow morning I shall show the method in
the mouths of patients at the Dental College of France. Dr. Herbst did
not patent his new method, to which may be given the name of "rotation
gold filling." All he desires is that every one may try the system,
and he feels himself already largely paid by the acknowledgments he is
daily receiving.

He proves that by his way of rotation one is able to adapt the gold
more perfectly to the walls of the cavity than by any other means
hitherto employed. One can thus work gold in the very weakest teeth,
because there is no force employed, yet the gold is as much condensed
as by any mallet known.

[Illustration]

The new instruments are very simple, and you may find them in the
dental depots. One can easily prepare them for himself--at least the
principal one, No. 5--by putting a broken burr in the hand-piece and
holding it like a pen for writing until the rotating end of the burr is
ground to a roof-like shape, on a dry Arkansas stone. Nos. 1, 2, 3, and
4 are smooth burnishers, and help to fix the first layers of gold in
large fillings. They are afterward used as finishers, Nos. 9 to 17 are
finishing burnishers, and No. 18 is a needle-point finisher.

The cavity is to be prepared in the usual way, but retaining points are
very much less needed than for other methods. Take, for instance, a
central cavity in a molar--and, moreover, the fundamental idea of this
system is to transform all cavities to be filled into central cavities.
Now fix several cylinders, of a size proportioned to the cavity, with a
common plugger, and then take No. 2, or 3, or 4, and by a slow rotation
polish the gold against the walls. If the gold does not stick directly,
put in more cylinders with the plugger, and recommence the condensation
with the burnisher. On this first layer of gold a second one is to be
made to adhere; but the polished surface prevents, and here No. 5 finds
employment in quick rotation and interrupted touches until the polish
is gone. (I may here remark that the gold is condensed by this rotation
and without pressure in a very remarkable way.) For large fillings, No.
5 is to have proportionate points,[13] which, if too fine, will make
holes in the gold, and the pressure is to be intermittent, in order to
avoid the development of heat, which would be painful and irritating to
the pulp.

[13] In the cuts, Nos. 6, 7, and 8 are proportionate modifications of
No. 5.

All the instruments by use get gilded, and will not work longer without
tearing out the gold; but this inconvenience may be prevented by
occasionally rubbing them while in rotation upon a piece of tin.

The filling of the cavity is continued in the way above described.

Let us now take the case of two incisors with lateral cavities
approximating one another. The two cavities, prepared as usual, are
treated as if one, and the gold is at the same time introduced into
both cavities, fixing some cylinders in the four corners by rotation
of the proper burnishers, and condensation with No. 5, until they are
filled, so that there appears to be a single mass of gold. No. 18 is
then pushed with regular rotation between the teeth until the mass
is quite separated, so that thin files, and disks, and tapes may be
employed in finishing the fillings.

In filling similar cavities between the second bicuspid and first
molar, after they are properly prepared, place a matrix and fill
one cavity with shellac to retain the matrix, and distribute the
resistance, and then fill the other like a central cavity, beginning at
the cervical border, and pressing especially against the matrix at that
point, work toward and finish at the middle of the crown. Having filled
the first one, remove the shellac and fill the other in the same way.

The rotation and the pressure, _if intermittent_, do not produce
heat--at least, not more than will render the gold cohesive.

Dr. Herbst filled for me two molars, carious to the cervical border,
and very sensitive there, for which reason they had for years been
filled with plastics, because I was afraid of perforation if retaining
points were made, without which gold filling by malleting would not
have been possible; and I was too nervous to sit three or four hours in
the chair. Dr. Herbst filled both teeth by rotation, without retaining
points, in a little more than one hour. Several gentlemen present have
seen them and observed the severe tests to which Mr. Brasseur subjected
them, and I may add that notwithstanding the great sensitiveness of
the dentine and the proximity of the pulps, I felt not the least
inconvenience from heat, and my own patients bear like testimony.

We will now split a crown filled in the hand, and you see that the
gold is pressed into the smallest depressions of the interior surface,
and is so uniformly condensed as to resemble an ingot, impossible
to separate in pieces, yet you may note the different stages of the
rotation.

I saw Dr. Herbst fill six cavities--some of them large ones--in front
teeth, taking altogether at the same sitting about one hour.

It would be difficult to precisely describe the manipulation requisite
for the great variety of cases presenting in practice, but I have
explained to you in theory the typical ones in the hope of stimulating
you to try this method of filling by rotation, which I look upon as one
of the most ingenious modes yet given to our profession. The results
are splendid, and the operator will thereby save much time and prevent
great suffering on the part of the patient.




DR. KOCH'S BERLIN LECTURE ON CHOLERA AND THE COMMA BACILLUS.


An important conference upon cholera was held in Berlin, at the
Imperial Board of Health, on the evening of July 26. There were present
Drs. Von Bergman, Coler, Eulenberg, B. Frankel, Gaffky, Hirsch, Koch,
Leyden, S. Neumann, Pistor, Schubert, Skrezcka, Struck, Virchow, and
Wollfhugel. The conference had been called at the instance of the
Berlin Medical Society, whose President, Professor Virchow, explained
that it was thought advisable Dr. Koch should in the first instance
give a demonstration of his work before a smaller body than the whole
Society, so that the proceedings might be fully reported in the medical
press. He mentioned that Herr Director Lucanus and President Sydow
had expressed their regret at being unable to be present, as well as
many others, including Drs. Von Lauer, Von Frerichs, Mehlhausen, and
Kersandt. Dr. Koch first showed various specimens of the bacilli and
their method of preparation (see _Berliner Klinische Wochenschrift_,
August 4). This resembles that for the tubercle bacillus, viz.,
drying on a cover glass and staining with fuchsin or methyl-olin.
Koch then gave a history of his work while in Egypt and India. His
post-mortem examinations led him to believe that the intestines were
the nidus of the disease. At first his microscopical examinations were
unsatisfactory, but finally he got fresh dejecta and acute cases, and
then discovered the comma bacillus.

This, he said, is smaller than the tubercle bacillus, being only about
half or at most two-thirds the size of the latter, but much more plump,
thicker, and slightly curved. As a rule, the curve is no more than that
of a comma (,), but sometimes it assumes a semicircular shape, and he
has seen it forming a double curve like an S; these two variations from
the normal being suggestive of the junction of two individual bacilli.
In cultures there always appears a remarkably free development of
comma-shaped bacilli.

These bacilli often grow out to form long threads, not in the manner
of anthrax bacilli, nor with a simple undulating form, but assuming
the shape of delicate long spirals--a corkscrew shape--reminding one
very forcibly of the spirochaete of relapsing fever. Indeed, it would be
difficult to distinguish the two if placed side by side. On account of
this developmental change, he doubted if the cholera organism should
be ranked with bacilli; it is rather a transitional form between the
bacillus and the spirillum. Possibly it is true spirillum, portions
of which appear in the comma shape, much as in other spirilla, _e.
g._, spirilla undula, which do not always form complete spirals, but
consist only of more or less curved rods. The comma bacilli thrive
well in meat infusion, growing in it with great rapidity. By examining
microscopically a drop of this broth culture the bacilli are seen in
active movement, swarming at the margins of the drop, interspersed with
the spiral threads, which are also apparently mobile. They grow also
in other fluids, _e. g._, very abundantly in milk, without coagulating
it or changing its appearance. Also in blood serum they grow very
richly. Another good nutrient medium is gelatine, wherein the comma
bacilli form colonies of a perfectly characteristic kind, different
from those of any other form of bacteria. The colony when very young
appears as a pale and small spot, not completely spherical as other
bacterial colonies in gelatine are wont to be, but with a more or less
irregular, protruding, or jagged contour. It also very soon takes on
a somewhat granular appearance. As the colony increases the granular
character becomes more marked, until it seems to be made up of highly
refractile granules, like a mass of particles of glass. In its further
growth the gelatine is liquefied in the vicinity of the colony, which
at the same time sinks down deeper into the gelatine mass, and makes a
small thread-like excavation in the gelatine, in the center of which
the colony appears as a small white point. This again is peculiar;
it is never seen, at least so marked, with any other bacterium. And
a similar appearance is produced when gelatine is inoculated with a
pure culture of this bacillus, the gelatine liquefying at the seat of
inoculation, and the small colony continually enlarging; but above it
there occurs the excavated spot, like a bubble of air floating over
the bacillary colony. It gives the impression that the bacillus growth
not only liquefies the gelatine, but causes a rapid evaporation of the
fluid so formed. Many bacteria also have the power of so liquefying
gelatine with which they are inoculated, but never do they produce such
an excavation with the bladder like cavity on the surface. Another
peculiarity was the slowness with which the gelatine liquefied, and
the narrow limits of this liquefaction in the case of a gelatine disk.
Cultures of the comma bacillus were also made in agar-agar jelly, which
is not liquefied by them. On potato these bacilli grow like those of
glanders, forming a grayish-brown layer on the surface. The comma
bacilli thrive best at temperatures between 30 deg. and 40 deg. C., but they
are not very sensitive to low temperatures, their growth not being
prevented until 17 deg. or 16 deg. C. is reached. In this respect they agree
with anthrax bacilli. Koch made an experiment to ascertain whether
a very low temperature not merely checked development, but killed
them, and subjected the comma bacilli to a temperature of -10 deg. C.
They were then completely frozen, but yet retained vitality, growing
in gelatine afterward. Other experiments, by excluding air from the
gelatine cultures, or placing them under an exhausted bell-jar, or in
an atmosphere of carbonic acid, went to prove that they required air
and oxygen for their growth; but the deprivation did not kill them,
since on removing them from these conditions they again began to grow.
The growth of these bacilli is exceptionally rapid, quickly attaining
its height, and after a brief stationary period as quickly terminating.
The dying bacilli lose their shape, sometimes appearing shriveled,
sometimes swollen, and then staining very slightly or not at all. The
special features of their vegetation are best seen when substances
which also contain other forms of bacteria are taken, _e. g._, the
intestinal contents or choleraic evacuations mixed with moistened earth
or linen and kept damp.

A most important statement was that the comma bacillus seems to be
killed by the bacteria of putrefaction, and consequently agents that
destroy the latter organisms without the former may really do injury,
by removing from the cholera bacillus an impediment to its growth.

As for destructive agents to the bacillus, he found it killed by
solutions in the following proportions: oil of peppermint, 1 in 2,000;
sulphate of copper, 1 in 2,500 (a remedy much employed, but how much
would really be needed merely to hinder the growth of the bacilli in
the intestine!); quinine, 1 in 5,000; and sublimate, 1 in 100,000.

In contrast with the foregoing measure for preventing the growth of
these bacilli is the striking fact that they are readily killed by
drying. This fact is proved by merely drying a small drop of material
containing the bacilli on a cover glass, and then placing this over
some of the fluid on a glass slide. With anthrax bacilli vitality is
retained for nearly a week; whereas, the comma bacillus appears to be
killed in a very short time.

Dr. Koch having found and cultivated the comma bacillus and ascertained
its distinctive character, next proceeded to investigate its relation
to cholera. In all there were now about one hundred cases of cholera
in which the bacillus had been found, while it was never found in
connection with other diseases. Three different views, said the
speaker, as to its relation to the cholera process are tenable:

1. That the disease favors the growth of these bacilli by affording
them a suitable soil. If so, it would mean that the bacillus in
question is most widely diffused, since it has been found in such
different regions as Egypt, India, and France; whereas the contrary is
the case, for the bacilli do not occur in other diseases, nor in the
healthy, nor apart from human beings in localities most favorable to
bacterial life. They only appear with the cholera.

2. It might be said that cholera produces conditions leading to a
change in form and properties of the numerous intestinal bacteria,
a pure hypothesis; the only instance of such a conversion refers to
a change of physiological and pathogenic action, and not of form.
Anthrax bacilli under certain conditions lose their pathogenic power,
but undergo no change in shape; and that is an instance of a loss of
pathogenic properties, while there is no analogy to support the view of
the harmless intestinal bacteria becoming the deadly cholera bacilli.
The more bacterial morphology is studied, the more certain it is that
bacteria are constant in their form; moreover, the comma bacillus
retains its special characters unchanged through many generations of
culture.

3. Lastly, there is the view that the cholera process and the comma
bacilli are intimately related, and there is no other conceivable
relation but that the bacilli precede the disease and excite it. "For
my own part," said Dr. Koch, "the matter is proved that the comma
bacilli are the cause of cholera."

Dr. Koch then described his attempts to inoculate lower animals with
the bacillus, and explained the cause of his failure in the natural
immunity of the animals against the disease.

In advocating the local Indian origin of the disease he said: That the
virus can be reproduced and multiplied outside the body is apparent,
since the bacillus can be cultivated artificially, and its growth is
not affected by comparatively low temperatures. Probably it does not
grow in streams and rivers, where, owing to the current, a sufficient
concentration of nutrient substance does not occur; but in stagnant
water and at the mouths of drains, etc., vegetable and animal refuse
may accumulate and afford the necessary nutriment. Thus is explained
the propagation of cholera by the subsoil water, and the increase of
epidemics with the sinking of its level, which lessens the flow and
diminishes the amount of surface water. Admitting the dependence of
cholera upon this micro-organism it is impossible to conceive the
disease having an autochthonous origin in any particular place; for a
bacillus must obey the laws of vegetable life, and have an antecedent;
and since the comma bacillus does not belong to the widely diffused
micro-organisms, it must have a limited habitat. Therefore, the
occurrence of cholera on the delta of the Nile does not depend on its
resemblance to the delta of the Ganges; but the disease must have
been imported there as it is into Europe. It was once thought that an
outbreak in Poland had a local origin until it was discovered to have
been introduced from Russia. Again, about ten years ago, there was a
sudden outbreak at Hamar (Syria), thought to be an instance of local
origin, but erroneously, as shown by a statement of Lortet, who told
Koch, when at Lyons, that the epidemic had been introduced into Hamar,
where he was at the time, by Turkish soldiers from Djeddah. All great
epidemics of cholera began in South Bengal, where the conditions for
the development and growth of the bacillus are most perfect.--_Med.
Record._




LOCAL ANAESTHESIA BY THE HYDROCHLORATE OF COCAINE.

By R. J. LEVIS, M.D., Surgeon to the Pennsylvania Hospital and to the
Jefferson Medical College Hospital.


The notes of a few cases of the use of the hydrochlorate of cocaine
will illustrate its perfect efficiency in some and its apparent
inertness in others, and may help toward its proper application and
general appreciation.

In a double extraction of hard cataract there was no pain produced by
the graspings of the conjunctiva in the fixation of the eyes, in the
corneal incisions, and in the iridectomies.

A 4 per centum solution was freely brushed over the entire conjunctival
surface three times, at intervals of ten minutes, and the operations
were commenced in forty minutes after the first application. No
irritation was produced, and the only sensation described was that
of "numbness and hardness." The entire conjunctival surface seemed
insensible to repeated pinching with the fixation forceps.

In a single extraction of hard cataract a 4 per centum solution was
brushed over the ocular and palpebral conjunctiva, with the eyelids
freely everted. Three applications were made at intervals of ten
minutes, and the operation was performed at the lapse of twenty-five
minutes. The patient asserted decidedly that she felt no pain whatever.

Preparatory to the operation for uterine procidentia and rectocele, the
vaginal and labial mucous surface was wiped dry, and a 4 per centum
solution of the hydrochlorate of cocaine was thoroughly brushed over
it. The sensitiveness was tested at three intervals of ten minutes
each, and the application was repeated three times. There appeared
to be at no time any decided loss of painful sensibility, and the
operation was finally performed under the anaesthesia of sulphuric ether.

For the removal of a rather large tarsal tumor, the ocular and
palpebral conjunctiva and the exterior of the eyelids were brushed with
the solution as previously used, at intervals of ten minutes, and the
excision was performed at the lapse of forty minutes. The operation
seemed to be as painful to the patient as if performed without an
attempt at anaesthesia.

For the operation for lachrymal obstruction the application was made in
the same manner and at the same intervals. The slitting of the punctum
and caniculus gave no pain, but the passage of the dilating probe down
the lachrymal canal seemed to produce some uneasiness.

Prior to applying nitric acid as a caustic to a syphilitic ulcer on the
tongue, the same manner and number of applications were repeated, the
tongue having been wiped dry and held protruding between the teeth. No
pain was produced on the thoroughly benumbed tongue.--_Med. News._




ON SEWAGE DISPOSAL.[14]

By Professor HENRY ROBINSON.


[14] By Professor Henry Robinson. Paper read Oct. 2, 1884, at the
Congress of the Institute held at Dublin.--_Building News_.

The outcome of several public inquiries which have taken place during
the last year or two, and of much valuable data derivable from other
sources, establishes, we think, a well marked advance with reference
to sewage disposal; and it may be of use, as well as of interest, if
we lay before this Congress the conclusions which, we conceive, are
deducible therefrom. We propose to deal with the subject under the
following heads: 1. Sewage disposal on land. 2. Sewage disposal by
chemical treatment. 3. Sewage disposal by discharge into a tidal river,
or into the sea, without treatment.


1. SEWAGE DISPOSAL ON LAND.

The object of dealing with sewage on land may be taken as twofold,
namely, to purify it (which is the sanitary object), and to utilize its
manurial products (which is the agricultural object). Where want of
skill or where prejudice has existed, these two have not been properly
separated, and the results have been in many cases unfavorable to
sewage disposal on land from either of the before mentioned points
of view. It has been regarded as an axiom that clay land cannot be
employed to clarify sewage. This is true when it is proposed to pour
the sewage on it as if the land were porous. Very recent experience,
however, has led to clay land being converted from an impervious to a
pervious condition, by which it has been successfully utilized. This is
effected by digging out the clay to a depth of about 6 ft., burning it
into ballast and replacing it in layers interposed with an occasional
layer of open alluvial soil, the whole area being well drained with a
free outlet for the effluent. We have successfully carried this plan
out, and with this result, that whereas it was not possible previously
to clarify the sewage of 100 people to an acre of clay land, the
prepared filtration area has been able to continuously clarify the
sewage of about 1,500 people to the acre. The cost of converting clay
land into this form of filter may be taken as varying from L750 per
acre to L1,000 per acre, according to local circumstances. One area
which we have just completed has cost L1,000 per acre. Before sewage is
passed on to these filters (or on to land) it should be strained so as
to remove the larger particles. The best arrangement for this purpose
is to pass the sewage upward through a straining medium (not downward),
and to run the solids from the bottom of the straining tank on to a
low lying piece of land for digging in as they are run out. Where such
a filtration area is made to form part of a sewage farm it acts as a
safety valve, and enables the land and crops to have a rest when they
do not require further irrigation; at the same time the process of
purification is not interrupted. If open, porous land is available for
sewage purification, and if it can be drained 6 ft. deep to a good free
subsoil, so that the effluent can get readily away, we find that the
sewage of from 600 to 700 people can be dealt with on each acre per
annum with both good agricultural and sanitary results.

In our address as President of the Engineering and Architectural
Section of the Congress of this Institute at Newcastle upon Tyne, in
1882, we directed attention to the important investigation which had
been conducted by Mr. R. Warrington, of Rothamsted, the result of which
was to show the action which goes on in the soil when sewage is passed
through it. Further information which the same observer has published
since that date is of equal value, and deserves to be read by all who
have to advise in regard to sewage disposal on land. The process of
"nitrification" (as it is termed), which he has so fully investigated,
consists in the conversion into nitrates (which serve to nourish plant
life) of the organic matter in sewage. This takes place by the action
of a living ferment of the bacteria family, which is created by and
feeds on the impurities in sewage, and these organisms both consume the
impurities and convert them into nitrates. The action of living agents
thus brings about the oxidation of the organic matter in sewage, just
as worms, larvae, fungi, and insects feed on the vegetable matter in the
soil, increasing the amount of nitrogenous material in it. Experience
during the past year or two has proved the feasibility of preserving
green crops in a succulent state by compressing them in silos, so that
they can be utilized for cattle fodder in the winter. This system
deserves notice in connection with sewage farming, as we are of opinion
that it will prove a valuable means of getting over the well known
practical difficulty which is experienced of finding a market for the
large amount of green crop which is produced by sewage irrigation. In
speaking of this system the term "silo" is applied to the artificial
chamber or receptacle for green crops (such as grass, vetches, clover,
etc.).

The term "silage" is applied to the crop thus treated, and the term
"ensilage" is applied to the process of making "silage." The details of
the construction of silos cannot be referred to here, beyond stating
that what is required is to construct a pit or chamber either in the
form of an excavation in the ground, with a brick or other lining, or
by building it above the ground. The object is to enable the green crop
to be deposited in an air and water tight chamber, in which pressure
can be applied to the crop to compress it. This is effected in some
cases by well treading the crop after it is laid in the silo, and then
spreading layers of earth to about a couple of feet, and pressing
the covering well down. Another way is to construct the silo with a
movable covering of the exact size and shape of its interior. This
cover is raised and lowered by suitable chains and rollers. After the
crop is placed in the silo, the cover is lowered and weighted so that
a thorough compressing is effected; the weight applied giving about
200 lb. or so per square foot of surface. Salt is sometimes added as
the crop is placed in the silo. A crop thus dealt with is stored for
months; when the silo is opened the fodder is found preserved, and in
a state readily taken to by cattle. It is desirable to choose the site
for the silos so that the fodder is preserved somewhere near the place
of consumption; also to lay out the works so that as little handling
as possible is required. For instance, the silo should be on sidelong
ground, so that the crop can be carted and tipped at a high level, and
the silage taken out for use at a lower level.


II. SEWAGE DISPOSAL BY CHEMICAL TREATMENT.

In the last edition of our book on "Sewage Disposal," in speaking of
precipitation we said that "the purification of sewage by chemicals
has been the subject of misapprehension, owing to the extravagant
advantages which have been claimed for the system by its advocates."
This is even more true now than it was two years ago, inasmuch as in
the recent scheme for dealing with the sewage of the Thames Valley
chemical treatment _per se_ was relied on to produce from the sewage
of a future population of 350,000 an effluent at all times fit to be
discharged at one point into the river Thames above London; but the
Parliamentary Committee rejected it. One part of the report of this
Committee deserves attention, when speaking of sewage treatment by
chemicals. It is as follows: "Your committee believe that in these
cases the process of filtering the chemically purified effluent through
earth ought, if possible, to be adopted, which was not provided for
in the scheme under their consideration." This opinion is exactly
in accordance with our experience, and is that which we have held
throughout. It is at the root of the whole matter, because efforts
are made by those interested in chemical processes to attain as high
a standard of purity as possible with the attendant heavy expense of
chemicals. Experience shows that it is impossible at all times and
seasons to be sure of a constant and uniformly high standard of purity,
and that chemical works should be supplemented by a filtration area,
however small. The addition of this, however, enables a lower standard
of effluent from the precipitation tanks to be admissible, and this can
be attained with very simple and inexpensive chemicals.

In the course of our practice we have had to advise as to the majority
of the processes, and to design the works for their being carried into
operation. We have found that the cost of such works complete varies
from 0.091 to 0.166 pound per head of the population, and that the
average cost of the works at several towns which we have been connected
with is 0.123 pound per head. This figure may be conveniently followed
by that of the cost of treatment, which we find varies from 0.036 to
0.110 pound per head per annum, and an average of several places gives
0.06 pound per head per annum. The above figures apply only to places
where the very highest standard was sought to be attained, but our more
recent experience leads us to modify the arrangement of the works and
the cost of treatment, so as to rely on filtration of the effluent as
an important factor. We estimate that under these conditions the cost
of the works complete would be about 0.075 pound per head, and the
cost of treatment 0.04 pound per head per annum. The disposal of the
sludge has always been a difficulty in these works, but this is now
overcome in two ways: either by digging it into the ground, as is done
at Birmingham now, or by pressing it into cakes in filter presses.
It is found at Birmingham that one ton of sludge with 90 per cent.
of moisture is produced from 1,000 people. There the lime process is
used. We have found that about one ton to 2,000 people is produced
where a salt of alumina or iron is used with the lime. At Birmingham
the sludge is dug into the land adjoining the works, and it is found
that one square yard of land will take one ton of sludge with 90 per
cent. of moisture once in three years, which results in three yards of
land being required to be provided for each ton of sludge. This system
of digging in sludge is successfully carried out as regards freedom
from nuisance. Where land is not available to dig in the sludge, it is
necessary to make it portable for removal and disposal away from where
it is produced. This is best effected by filter presses. Appliances are
made for this purpose, by which the sludge is pressed to a consistency
of about 50 per cent. of moisture. The cost of effecting this is about
0.007 pound per head per annum. It is found in practice that where the
sludge is produced by straining the solids from sewage before passing
it on to land for purification, it requires a little lime to enable
the press to work well. About two barrow loads of lime for each ton of
pressed sludge suffices.

It has been thought that the cost of precipitation would be covered,
and even a profit gained, by the sale of the sludge. This hope,
however, is not nearer realization now than it was in the time, now
gone past, when chemical processes were relied on to turn sewage from
a profitless into a profitable commodity. There is, consequently,
less justification now than there was at that time for adopting a
precipitation system for sewage disposal. It is entirely a question
of carefully considering the engineering and financial points
involved, regardless of the sanguine representations of interested
or enthusiastic advocates of any particular system. As the estimated
manurial value of the sludge which is precipitated from sewage by the
addition of chemicals does not seem to be capable of realization,
we think that probably the reason may be found in the fact that the
chemicals arrest that process of decomposition which is essential to
the conversion of the organic matters into nitrates for vegetation to
utilize.

This explanation will be understood in the light of what we have
already described in regard to "nitrification." If this view is
correct, it would follow that the more completely and permanently
the sludge is deodorized by the chemicals, the less capable is it of
passing through the necessary stages of decomposition by which its
manurial value can be realized. As mistakes are constantly being made
in regard to the weights of sludge with varying degrees of moisture,
the following table may be useful:

  Tons.            Per cent.           Tons.   Per cent.
   100 of sludge with 90 of moisture = 50       with 80
   100       "         "         "     33.3       "  70
   100       "         "         "     25         "  60
   100       "         "         "     20         "  50
   100       "         "         "     16.6       "  40
   100       "         "         "     14.3       "  30
   100       "         "         "     12.5       "  20
   100       "         "         "     11.76      "  15


III. SEWAGE DISPOSAL BY DISCHARGE INTO RIVER OR SEA.

We will next deal with the conditions which should be fulfilled where
it is sought to utilize a river or the sea into which to cast the
sewage of a town. If it can be ascertained beyond question that at the
proposed point of discharge the currents at all times will carry the
sewage right away, and will not at the same time produce mischief at
a distance (which is often omitted from the consideration), then that
arrangement may be accepted as a good one. This, however, seldom occurs.

A river has been looked upon by manufacturers and local authorities
as the natural carrier of their refuse from their district. This view
has been persevered in, in spite of the River Pollution Prevention Act
of 1876, which is practically a dead letter. The public, however, who
use a river either for pleasure purposes or for obtaining their water
supply, have of late years grown more and more united in their efforts
to stop this abuse; and there is no doubt that these efforts will
eventually succeed. In a paper which we read last year at the Congress
at Glasgow, we pointed out the steps that were necessary to be taken
to render this act operative, and we refer our hearers to that paper
if they wish to follow the matter further. The effect of discharging
sewage matter into a river has been the subject of much controversy
among chemists. Some allege most positively that the injurious
properties in the sewage are indestructible. This has led to alarmists
demanding that under no circumstances ought sewage to pass untreated
into a river.

We have given considerable attention to this vexed question, as it
requires to be grasped by any engineer who has to advise on the
selection of sewer outfalls, and it appears to us that the balance of
evidence is against the alarmists. Every river has a certain power of
oxidizing impurities in proportion to the extent of oxidation of the
river itself. Besides this, there are the powerful purifying influences
exercised by the plants and animalcules which exist in rivers.

It has been ascertained that entomostraca consume dead animal matter;
and where this is wanting they do not live, but where it is in
abundance they thrive. It follows, then, these minute animals exercise
an important function in absorbing sewage impurities. They multiply
prodigiously in these impurities, and are both created by them and fed
upon them, converting foul and dangerous matters into harmless ones, in
a similar way to that which we have referred to as nitrification when
speaking of the action of bacteria in the soil. Considering that these
organisms arise from and are fed on concentrated filth, it is obvious
that they cannot live when the conditions favorable to their existence
disappear. This would be the case when the sewage is discharged into a
large volume of water with a different temperature to that which suits
them, and with powerful oxidizing influences at work. These conditions,
added to the difficulty they must experience to find their natural
food--namely, concentrated sewage--where the sewage matter becomes so
greatly diluted, accounts for the fact that in a short run of a good
river sewage impurities largely disappear. The action of weeds and
plants also aids purification to a very large extent. Minute plants,
such as confervoid algae and the like, also assist in oxygenating the
river, as when exposed to light they decompose carbonic acid, and
liberate oxygen.

The practical question which has to be answered in every case where
sewage is proposed to be discharged into a river requires to be
approached from two points. The first is whether a nuisance will be
caused at the spot to which objection would be taken. If this is likely
to be the case, then the fact that the sewage will get purified in a
short run of the river does not meet the objection. The second point
requires a careful consideration of the condition of the river, both
from an engineering as well as from a chemical and biological point
of view. Decisions on these matters have too often been arrived at
in a rough and ready way. They require skillful treatment, as the
interests--both commercial and hygienic--which are affected are too
great to permit of them being dealt with by any who are not well
informed and careful. The general conclusions which we deduce from our
observations are as follows:

1. That chemical precipitation is not so necessary now as it was
considered to be a few years ago, in cases where land for irrigation is
not procurable.

2. That the efforts to profitably remove the manurial elements from
sewage by chemicals not having been successful, the system should be
adopted _per se_ only where a filtration area cannot be obtained.

3. That the success which has attended the construction of filtration
areas where the land is clayey, and the successful results which have
been obtained from a combined straining of sewage and of subsequent
filtration through small areas of artificial filters, point to the
adoption of one or other of these systems in many cases where chemical
treatment would previously have been advised.

4. That the injurious effects of passing untreated sewage into a river
depend upon not merely the relative volumes of the sewage and the
river, but chiefly upon the power of the river to oxidize the sewage,
which power is in proportion to the extent of oxidation of the river
itself.




NEW YORK CITY STREET CARS.


An article in the local news columns of the _Tribune_ says:

The loud outcry made a few years ago against the old fashioned plush
covered spring cushions, then used in street car for seats and backs,
caused them to be removed and set car builders at work to make a car
that would be light, healthy, and comfortable. The general plan of
perforated wooden seats with plain backs has been adopted by all the
companies. They are covered with a fine quality of heavy Axminster
carpet during the winter, and in the summer nearly all the cars have
only wooden seats and backs. Open cars are used on a number of routes
during the summer, and this is conducive to the health of passengers.
The only particular difference in the furniture of the cars is the mats
used on the floor. Seven of the lines use sectional wooden mats of
plain or ornamental design, while three retain cocoa mats. Wooden mats
are the easiest to clean. Cocoa mats retain moisture on damp or rainy
days, and emit a musty odor. There are four sets for each car, and they
are changed every trip on rainy days.

The First and Second Avenue routes, under one management run 150 cars;
the Third Avenue, 180; the Fourth, 75; the Sixth, 88; the Broadway and
Seventh, 135; the Eighth and Ninth, 160; and the Tenth, 120. At the
stables of each the same general arrangement for cleaning cars is used,
while the details only are different, being regulated by the judgment
and experience of superintendents. From six to fifteen men are employed
for cleaning cars by the different companies.

After every round trip that a car makes, it is taken to the stable, the
mats are taken off the floor, and two men with brooms and specially
constructed brushes give it a thorough sweeping and brushing. After
a car makes its last trip at night, it is run upon what is termed
the washstand, which is a large turn table surrounded by hydrants.
Everything movable is taken out of it, and water is played from a hose
on the inside and outside, while four men with scrubbing brushes and
stiff brooms remove whatever dirt has accumulated during the day. After
this operation the car is run upon a side track, and two men dry the
inside and polish the windows.

While passengers find fault with the untidiness of street cars,
superintendents have a word also of complaint against passengers. If
men would not convert a car into a spittoon for the reception of cigar
stumps, tobacco spit, and quids, and a garbage box for nut-shells,
fruit rinds, cores, and pits, the remnants of lunches and old papers,
it would be much easier to keep up a cleanly appearance. Section 167 of
the Sanitary Code, which provides that no soiled article of clothing
or bedding shall be carried on street cars, except on the front
platform, is strictly enforced by all the companies, and it is worth a
conductor's position if he is proved derelict in this respect.

Nearly all the car companies build their own cars, and all have repair
shops at their stables, and as soon as a car is damaged by a collision
it is sent at once to the shop and repaired. Men are detailed to keep a
strict watch over all the working parts of cars.

No metal or plate has yet been found of which to make a hand railing
that will keep bright and untarnished. Many experiments have been
tried, but the hardest plate that can be obtained will not stand the
friction of the hands longer than two months, before the plated metal
will show through. Cars are painted and varnished at least once a year.
The various parts of the car last different periods. The wheels average
about eighteen months on long routes; on short routes, about two years.
Steps and platforms last about five years. There is no particular limit
for the floors and framework, as they are but little worn. Cars are
frequently built up from an old floor or framework, but at the end of
about fifteen years there is but little left of the original car.




RINGS OF SMOKE.


[Illustration: FIG. 1--APPARATUS FOR PRODUCING RINGS OF SMOKE.]

When, by means of a tube of from 2 to 5 millimeters in diameter, we
gently blow tobacco smoke against a wet pane of glass, we produce very
fugitive rings. If we operate with a closed vessel the rings are fixed,
the current being itself uniform. But the experiment that shows the
phenomenon perfectly is the one that consists in rendering the current
automatic by means of an aspirator--an arrangement analogous to that
devised by Mr. Nickles for analyzing the flame of a candle. A tapering
glass tube or, better, a metallic blow pipe traverses a cork which
hermetically closes a large bottle having a cock beneath and filled
with water (Fig. 1). The nozzle of the blow pipe entering the center
of the flame, and the cock being open, the liquid flows, and a column
of white smoke descends vertically to the surface of the water, where
it forms several concentric rings whose relief soon increases with the
thickness of the heavy smoke, which finds no exit. These rings have a
diameter so much the greater in proportion as the current is stronger
(Fig. 2).

Unfortunately, the number of the rings soon diminishes in measure as
the stratum of smoke that remains upon the surface of the water becomes
thicker. Finally, there remains but a single ring, which has a
thickness in the center of more than 0.015 m. (Fig. 3).

[Illustration: FIGS. 2 TO 5.--DIFFERENT ASPECTS OF RINGS OF SMOKE.]

Instead of the smoke of a candle, we may employ that of a cigar or of
a tobacco pipe. We thus avoid a deposit of fatty matter, which, in the
first case, soon clogs up the tube, if it is too fine a one, and thus
puts a stop to the experiment.

Several circumstances are known under which rings or crowns are
produced. (1) For example, in the spontaneous combustion of
phosphureted hydrogen, the resulting white vapors of phosphuric acid
rise, and roll round in horizontal white crowns when the air is calm
(Fig. 4). These crowns, whose diameter keeps on increasing, end by
separating into strips that dissolve in the humidity of the air. (2)
The crowns that we sometimes observe in calm weather around cannons
at the moment of firing have the same origin, although they are of a
different nature, and spread horizontally to a certain distance. With
vertical howitzers the crowns are horizontal, and very beautiful when
seen from beneath, since they rise vertically. (3) As well known,
a cardboard box having two apertures in the center of two opposite
sides, when filled with smoke and struck upon one of these sides,
allows the escape through the opposite aperture of curling rings of
smoke. (4) Steam escaping into the open air, through the intermittence
of a vertical eduction pipe, sometimes makes its exit in the form of
circular or elliptical crowns.--_La Nature._




AN IMPROVED HYACINTH GLASS.


The hyacinth is a native of the East. When it was introduced into
England, in 1596, only four varieties of it were known, but the Dutch
gardeners soon made wonderful progress in its culture, and, along
toward the end of the sixteenth century, had produced at least two
thousand varieties.

This plant is well adapted for house decoration in winter, when flowers
are rare. Its culture requires but little care. When the bulbs have
taken root in a dark place they are gradually brought into the light,
and placed where the temperature is moderate.

[Illustration: FIG. 1.--HYACINTH GLASS. FIG. 2.--DETAILS.]

Is a regular changing of the water favorable to the development of
this plant? Many florists doubt it, and it is often recommended not to
change the water, but only to replace that which has been lost through
evaporation. Others are of a contrary opinion, and assert that the
less favorable results that are obtained when the water is changed are
merely due the fact that the roots are injured when the plant is taken
out of the glass.

With the old style of glasses it has always been difficult to renew the
water regularly and keep the glass clean, but this inconvenience has
disappeared in the glasses invented by Mr. J. C. Schmidt, of Erfurth.

Fig. 1 represents one of these glasses, and Fig. 2 shows the details.
As may be seen, the tube, a, which contains the bulb, may be removed
from the glass, b, without the plant being touched or its roots
disturbed. The glass, b, may thus be easily cleaned and filled with
fresh water as often as necessary.--_Science et Nature_.




THE BOTANICAL CLUB OF THE AMERICAN ASSOCIATION.


The meeting of the American Association last year at Minneapolis
attracted a larger attendance of botanists than usual. Without much
consultation, a meeting of those interested in botany was called,
a president and a secretary were chosen, and discussions, short
communications, and papers upon botanical subjects listened to. The
Botanical Club was thus inaugurated; and before the close of the
session it was decided to do what was possible to secure a larger
attendance of botanists at the next gathering in Philadelphia.

Although during the interim the prospect of a good attendance at the
Philadelphia meeting had been fair, the most sanguine were surprised
to find that, as early as Monday preceding the opening, a number of
botanists had arrived in the city; and by the following day a larger
gathering could have been assembled than the total attendance at
Minneapolis.

The first meeting of the club, of which several were held between
Friday and Wednesday, was responded to by an attendance of about
thirty--a little below the average attendance for the subsequent
meetings. Prof. W. J. Beal, of Lansing, Mich., the president,
took the chair; and Prof. J. C. Arthur, of Geneva, N. Y., was
appointed secretary to fill the vacancy caused by the absence of
Professor Coulter. A paper by Dr. N. L. Britton, of New York, on the
composition and distribution of the flora of New Jersey, was read.
The surface-features of the State were given, and the corresponding
vegetation described. The work of cataloguing the plants is being done
under the supervision of the State geological survey. The list at
present has reached the very large total of nearly fifty-five hundred.

Prof. C. R. Barnes, of La Fayette, Ind., spoke of the course of the
fibro-vascular bundles in the leaf-branches of Pinus sylvestris. The
two needle-leaves at the end of each short lateral axis contain each
a paired bundle. The question at issue was whether this structure
represented one or a pair of bundles, or whether it might not be a
segment of the fibro-vascular ring of the stem. A study of the early
stages shows that the first change in the stem is to divide the
fibro-vascular ring into halves at right angles to the plane of the
leaves; and subsequently these divide again, sending one branch of each
to each leaf. The paper led to much discussion by Professors Buckhout,
Macloskie, and others.

Dr. Bessey, of Ames, Ia., described the opening of the flowers of
Desmodium sessilifolium. They expand partially in the usual manner,
then remain stationary till a particular sensitive spot at the base of
the vexillum is touched by an insect, when the wings and keel descend
with a jerk, the stamens are released, and the insect dusted with
pollen.

Professor Mackloskie, of Princeton, N. J., described the method of
cross-fertilization of Geranium maculatum by bumblebees. Professor
Dudley, of Ithaca, N. Y., spoke of the torsion of stems of Eleocharis
rostellata, and also on the protogynous character of some species of
Myriophyllum. Mr. William H. Seaman, of Washington, D. C., advocated
the use of rather thick oblique sections in studying the structure of
the fibro-vascular bundle--a method that called forth a very strong
protest.

Professor W. J. Beal gave a paper concerning the manner in which
certain seeds bury themselves beneath the soil, which was discussed
by Professors Bessey, Rothrock, and others. A paper by Prof. W. R.
Lazenby, of Columbus, O., on the prolificacy of certain weedy plants,
embraced careful estimates of the average number of seeds produced by
individual plants among various kinds of weeds. Dr. J. T. Rothrock, of
Philadelphia, addressed the club on some phases of microscopic work,
alluding particularly to microscopic work, alluding particularly to
micro-photography, its importance to the investigator, and the ease of
execution.

Dr. Asa Gray called attention to the interesting discovery of Mr.
Meehan regarding the mode of exposing the pollen in the common
sunflower. He had found that, contrary to the teachings of the text
books, the pistil and stamens develop together until reaching full
length, when the filaments rapidly shorten, and the anther tube is
retracted, exposing the style covered with pollen, the further changes
being the same as usually stated. This Mr. Meehan construed to be a
device for self-fertilization; while Dr. Gray showed that, although
bees carried pollen from one flower to another of the same head, they
also carried it from head to head, which constituted crossing in the
fullest sense. An interesting discussion followed, in which Professor
Beal suggested that an excellent experiment would be to cover up the
heads and ascertain if any fertile seeds were produced. Dr. Gray
thought it very likely there would; for, when cross-fertilization is
not effected, self-fertilization often takes place. Mrs. Wolcott had
proved this to be so; for, in covering up the flowers to keep birds
away, she found that plenty of seeds were formed.

Dr. George Vasey, of Washington, gave some notes on the vegetation of
the arid plains, which was followed by observations on the curvature of
stems of conifers by Dr. Bessey, in which he noted the bending of stems
one, two, and even three years old.

Mr. THOMAS MEEHAN discussed the relationship of Helianthus annuns and
H. lenticularis; showing that there was a constant difference in the
form of the corollas, the former being campanulate, and the latter
tubular. The two are treated as one species in Gray's Synoptic Flora of
North America; the one being considered a cultivated form of the other,
a view from which the speaker dissented. Mr. Meehan then spoke upon
the fertilization of composites; concluding that the arrangements were
such as to favor self-fertilization, which is opposed to the generally
accepted view.

Prof. L. M. Underwood, of Syracuse, N. Y., gave some statistics
concerning the North-American Hepaticae. Of the two hundred and
thirty-one species found north of Mexico, a hundred and twenty are
pecular to America; fully one-half the latter are not represented in
any public or private herbarium in this country.

In a paper on the nature of gumming, or gummosis, in fruit-trees, Prof.
J. C. Arthur detailed experiments from which the conclusion had been
reached that it was due to a deorganization of the cell-walls of the
tree through the influence of some fungus, but not necessarily of a
specific one.

It had been produced experimentally by the bacteria of pear-blight
and by Monilia fructigenum, the fruit-rot fungus; although the most
common cause is doubtless the Coryneum, first described by Oudemans in
Hedwigia.

At the final meeting the Committee on Postal Matters then gave its
report. This committee was appointed at Minneapolis to inquire into
the various obstructions which the postal authorities throw in the way
of exchanging specimens of dried plants. The efforts of the committee
had been directed toward securing the passage of specimens bearing
the customary written label at fourth-class rates of postage. The
Decision of the Postmaster-General was read, stating that the present
law could not be construed to permit the passage of specimens with
written labels except at letter-rates, but expressing a willingness to
bring the matter, at the proper time, to the attention of Congress,
the Canadian authorities, and the congress of the Universal Postal
Union. Some discussion followed; and a motion was carried to continue
the committee, and also instructing the president and secretary of the
club to draft resolutions to be presented to the section of biology, in
order to still further promote the objects in view.

These resolutions were acted upon by the biological section on the
following day. Dr. Bessey was chosen president, and Professor Arthur
secretary, for the next year.

Besides the reading of papers, the club took several excursions. On
Saturday they went to the pine-barrens of New Jersey, about fifty
participating. On Monday a party visited the ballast-grounds during
the morning, and upon their return inspected the library and herbarium
of Mr. I. C. Martindale, of Camden, N. J. In the evening of the same
day the Botanical section of the Philadelphia Academy of Science
entertained the club, the Torrey Botanical Club of New-York City, and
other invited guests, at the rooms of the Academy. About three hundred
were present, and a thoroughly enjoyable time experienced. On the
afternoon of Tuesday the club and its friends, in all about eighty,
made an excursion to the Bartram Gardens, one of the most interesting
historical spots to botanists in this country; and the club then
adjourned.

In reviewing the attendance of botanists in Philadelphia, and the work
of the Botanical Club, there is much reason for congratulation. About a
hundred entered their names on the register of the club as botanists,
or about eight per cent. of the total attendance, one-half of whom
are widely known for their attainments in the science. There was no
lack of interesting papers and free discussion. Besides the important
measures already referred to, the club was instrumental in securing the
appointment of a permanent committee of the Association to encourage
researches on the health and diseases of plants. But, above all, the
augmented facilities for intercourse and acquaintanceship, and the
impulse imparted to individual workers, through the influence of the
club, are a sufficient _raison d'etre,_ and a promise of usefulness of
the future.--_Science_.




PETROLEUM WELLS.


The theory of artesian and of spouting petroleum wells is entirely
different. While the latter owe their operation to an internal
pressure, due to gases accumulated within a confined space, the former
are due to the pressure of a liquid which is flowing--a pressure caused
by a sheet of water of unequal height; and they spout with so much
the more force in proportion as the difference of level between the
orifice and starting point of the sheet of water is greater.

Petroleum reservoirs, or pockets, contain, along with the petroleum,
gases, salt water, sand, and foreign substances of varying nature. The
liquids and gases in these pockets are often submitted to very great
pressure. If we make an aperture in the pocket, there will occur, by
reason of the tension, and according to the location of the aperture,
a sudden exit of gas, petroleum, salt water, etc. Yet it may happen
that as the sounding well has been bored through the upper part of the
pocket, where the gases are accumulated, only the latter will make
their exit without any trace of petroleum. Under such circumstances
the appearance of inflammable gases at the surface indicates pretty
certainly the presence of inflammable liquids in the region explored,
and will justify further exploration or the fitting of suction pumps to
the well holes.

It will be understood that a natural flow of petroleum will occur only
so long as the pressure is sufficient, and that a pocket may cease to
give mineral oil spontaneously, even though it may still contain large
quantities of it. This is the reason why at present spouting wells are
not abandoned when they cease to operate, but are worked by lift pumps.
The three diagrams, 1, 2, and 3, will give an idea of the different
configurations that petroleum pockets may present. In No. 1, as the
well hole reaches the summit of the gas chamber, the gases alone will
be forced to the surface by reason of the internal pressure, and not
the slightest trace of petroleum will accompany them.

In No. 2, as the well ends at the side of the pocket, only a portion of
the petroleum--that which is included between the dotted lines--will
come to the surface.

In No. 3, as the well ends at the lowest extremity of the pocket,
nearly the entire contents of the latter will be forced out naturally.
It results from this that in petroleum exploitation the sudden
appearance and disappearance of the spouting in no wise proves that the
pocket is exhausted.--_Science et Nature_.

[Illustration: CONFIGURATION OF PETROLEUM POCKETS.]




ALUMINUM AND ITS ALLOYS.


Symbol, Al. Equivalent, old, 13.7; new. 27.49. Specific gravity, cast,
2.46. Hammered, 2.67. Specific heat, 0.2143, Heat conductivity, 0.66 on
silver scale = 100.

Melting point, 1,250 deg. or 1,560 deg. Fah., according to different
authorities.

A shining, white, sonorous metal, having a shade between silver and
platinum. It is malleable and ductile, does not oxidize when exposed to
dry or moist air, and is not chemically affected by hot or cold water.

Sulphureted hydrogen gas, which so readily tarnishes silver, has no
action upon this metal.

Having but one defect in its uses as a pure metal (difficulty in
soldering), it enters largely as an alloy of other metals, making
the baser metals more valuable in resisting oxidation, and as a good
as well as cheap imitation of the precious metals.

Its power to ameliorate the condition of the alloys of copper, zinc,
tin, iron, nickel, silver, gold, and platinum by portions sometimes
less than a thousandth part is beautifully illustrated in the elegant
articles of tableware, bric a brac, and ornamental hardware now
coming upon the commercial market. Its uses in the mechanic arts in
the various forms of bronzes in filling a long wanted requirement of
combined ductility, strength, sonorousness, and freedom from oxidation,
thus giving to its alloys a high value for articles of house hardware,
carriage and harness trimmings, quick running machinery, journal
bearings, propeller blades, and artillery. Piano wires made from its
alloys will vibrate ten seconds longer than the best now in use.

For the kitchen and for articles for the toilet, there is no more
beautiful and cleanly ware. An alloy of silver 20 and aluminum 80 parts
by weight, for nautical and other instruments, is without a rival in
beauty and lightness; the sea air does not tarnish it.

The aluminum-silver alloys are more valuable than pure silver for table
service; its wares will not be destroyed by the constant polishing that
wears out our plate, and holds an immunity from the destructive effects
of the fatty and acetic acids.

For watch cases it wears cleaner than pure silver, and for watch
movements it is far superior to the brass and nickel or German silver
heretofore used. An alloy is now made in France that has elastic
qualities equal to steel for watch springs, and with the valuable
property of being free from magnetic effect.

The aluminum bronzes, when combined with five per cent. of gold, have
all the beauty, finish, and durability of color of eighteen carat gold;
they are entering largely into the manufacture of watch cases and
jewelry.

The composition most approved is made of copper 85, aluminum 10, gold
5, parts by weight. This can be soldered with any of the jeweler's
solders of gold, silver, and zinc in the usual way.

The most important alloy, _aluminum bronze_, is composed of aluminum
10 parts, copper 90 parts by weight; specific gravity, 7.7. It has a
pale gold color, harder than ordinary bronze, takes a fine polish, is
malleable and ductile, but when rolled into sheets requires annealing
at every third passage through the rolls, and when drawn into wire must
be frequently annealed. It may be forged cold or hot, and can be drawn
in tubes. In wire it has a tensile strength of 100,000 lb.

This alloy is often found to be brittle at the first mixing, but
becomes ductile after remelting. It is softened while being worked by
plunging in water at a low red heat.

The Parisian gold colored alloy is made of aluminum 10.7, copper, 89.3,
by weight; used much for cheap French jewelry.

A non-oxidizable alloy in a moist atmosphere: Aluminum, 25, iron 75
= 25 per cent. aluminum. A hard bright alloy, with the properties of
silver: Silver 5 (by weight); aluminum 95 = 5 per cent. aluminum.

The silver alloys with aluminum bronze, as represented in the four
following atomic formulas, are of a rich gold color, and well adapted
for jewelry, watch cases, etc.:

                           Cu       Al       Ag
  Ag + 24 (Al + Cu_{6}) = 0.9180 + 0.0616 + 0.0203
  Ag + 24 (Al + Cu_{7}) = 0.9241 + 0.0570 + 0.0188
  Ag + 24 (Al + Cu_{8}) = 0.9330 + 0.0504 + 0.0166
  Ag + 24 (Al + Cu_{9}) = 0.9400 + 0.0450 + 0.0150

The figures being proportional weights.

A cheap alloy for journal boxes and machinery may be made by
substituting zinc for silver in the following atomic proportions:

                           Cu       Al       Zn
  Zn + 2(Al + Cu_{6})  = 0.8643 + 0.0622 + 0.0734
  Zn + 2(Al + Cu_{9})  = 0.9053 + 0.0435 + 0.0512
  Zn + 2(Al + Cu_{12}) = 0.9273 + 0.0333 + 0.0394

This is subject to considerable shrinkage in casting, but is tenacious,
and when drawn into wire has a tensile strength of ninety to one
hundred thousand pounds.

The following alloys, in which iron enters as a third element, are well
adapted for gun metal, being hard, tenacious, laminable, and ductile:

                          Cu       Al       Fe
  Fe + (Al + Cu_{15}) = 0.9203 + 0.0267 + 0.0530
  Fe + (Al + Cu_{9})  = 0.9399 + 0.0446 + 0.0149

Also a four-element alloy of

                                  Cu       Al       Zn       Fe
  1. Fe + Zn + (Al + Cu_{12}) = 0.8386 + 0.0305 + 0.0712 + 0.0600
  2. Fe + Zn + (Al + Cu_{15}) = 0.8666 + 0.0249 + 0.0588 + 0.0496

The tensile strength of the above alloys as drawn wire is 82,000 pounds
for the first, and 107,000 pounds for the second.

All of the alloys in which zinc or zinc and iron enter in place of
silver, the color is affected and the luster diminished.

With nickel and platinum for the third element, we have:

                            Cu       Al       Ni
  Ni +  6 (Al + Cu_{6}) = 0.9129 + 0.0634 + 0.0237
  Pl + 21 (Al + Cu_{6}) = 0.9117 + 0.0656 + 0.0225

Those alloys into which platinum is introduced are less affected by
acids than those in which silver takes the place of platinum; platinum
producing a higher luster than silver.

In the alloys of aluminum bronze with the more difficultly fusible
metals, it is preferable to fuse the bronze first, then add the other
metal in small shavings or wire; by this means the less fusible metal
absorbs the other without raising the heat of the furnace excessively.
Add the least fusible metal last, a little at a time, allowing the heat
of the melted metal to fall by degrees, which prevents boiling and
evaporation. The crucibles for mixing the alloys should be of plumbago
lined with a paste of lime.

Avoid sand crucibles, as silicium may be reduced and absorbed by the
aluminum, inducing brittleness. If found brittle, remelt with cryolite
as a flux, or stir the melted metal or alloy with a hard wood stick
that has been slightly charred.

In adding aluminum to the copper, cut it in small pieces and push it to
the bottom of the crucible with a dry, hard wood stick split so as to
hold the pieces.

Sodium chloride (common salt) calcined to evaporate the water, and
caustic soda with pulverized charcoal, may be used as a flux for pure
aluminum. Avoid borax as a flux, as its metal may suffer reduction,
making the aluminum brittle. Aluminum will alloy with tin alone, but is
liable to separate on refusion. Does not alloy with lead.

Bismuth, even in minute quantity, makes these alloys brittle.

The East Indian steel called _wootz_ is, according to analysis, alloyed
with aluminum. No reliable solder has yet been found for pure aluminum
that will flow freely under the blow pipe or from a soldering iron.

A process recently adopted in France is to plate the parts to be united
with alloys of tin 5, aluminum 1, upon which tin solder will flow.
These proportions may be slightly varied to suit requirements for
hardness.

Harder solders to be used with a blowpipe may be made with alloys of
zinc, tin, and aluminum.

Aluminum is now made at the works of M. Deville, at Javelle, near
Paris, and at Salindres, France; also at Birmingham, England. The
product of late has reached the value of $20,000 annually in Europe.
It has been claimed to be made in Philadelphia at a reduced cost. The
present price in New York is $1.25 per oz. As its bulk is over four
times as great as silver, its comparative cost is but one-third that of
silver--a point not often considered when the price is quoted.

       *       *       *       *       *

A CATALOGUE containing brief notices of many important
scientific papers heretofore published in the SUPPLEMENT,
may be had gratis at this office.

       *       *       *       *       *




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       *       *       *       *       *


  TABLE OF CONTENTS.

                                                                    PAGE

  I. CHEMISTRY AND METALLURGY.--Determination of Tannin.--By
    E. JOHANSON.                                                    7458

    The Incomplete Combustion of Gases.--By H. B. Dixon.--Abstract
    of paper read before the British Association at Montreal.       7458

    Aluminum and its Alloys.                                        7462


  II. ENGINEERING AND MECHANICS.--The New Dam at Suresnes.--With
    engraving.                                                      7453

    Brearey's Aeronautical Machine.--With engraving.                7453

    Raising of the Fallen Girder of the Douarnenez Viaduct.--2
    engravings.                                                     7454

    Improved Wire Testing Machine.--With engraving.                 7454

    Improved Doubling and Laying Machine.--With engraving.          7454

    Boiler Tubes.                                                   7455

    Improved Ladle Carriage.--2 figures.                            7455

    The Repair of Boiler Tubes.--11 figures.                        7455

    Grulet's Screw for Raising Water.--1 engraving.                 7456


  III. TECHNOLOGY.--On Various Toning Baths.--Several
    experiments.--By W. M. ASHMAN.                                  7456

    Coating Plates with Gelatine Emulsion.--5 figures.              7457

    Iodo-chloride of Silver Emulsion.--By V. SCHUMANN               7458
    Apparatus for Saturating Water with Sulphurous Acid.--1
    engraving.                                                      7458


  IV. PHYSICS, ELECTRICITY. ETC.--The Wave Theory of Light.--By
    SIR WM. THOMSON.--Sound and light due to wave
    vibrations.--Difference between vibrations of light and
    sound.--Radiant heat.--Solar spectrum.--Luminiferous
    ether.--How to measure wave lengths of light and the frequency
    of vibrations.--With diagrams.                                  7448

    The Limitations of Submarine Telegraphy.                        7450

    Williams' System of Coast Defense by Electrical
    Torpedoes.--Full page of figures.                               7451

    New Electric Gas Lighter.--2 figures.                           7452

    Insulators for Telegraph and Telephone Lines.--9 figures.       7452

    Electric Light in Theaters.                                     7452

    Rings of Smoke.--5 figures.                                     7461


  V. ARCHITECTURE.--The New Technical High School at
    Berlin.--With engraving.                                        7447

    The New University Buildings at Strassburg.--2 engravings.      7447


  VI. BOTANY, ETC.--An Improved Hyacinth Glass.                     7461

    The Botanical Club of the American Association.                 7461


  VII. HYGIENE, MEDICINE, ETC.--Herbst's Method of
    Filling.--Demonstrated by Dr. G. C. CLUDINS.                    7459

    Dr. Koch's Berlin Lecture on Cholera and the Comma Bacillus.    7459

    Local Anaesthesia by the Hydrochlorate of Cocaine.--By R. J.
    LEVIS, M.D.                                                     7459

    On Sewage Disposal on Land, by Chemical Treatment, and by
    Discharge into River or Sea.--By Prof. H. ROBINSON              7460


  VIII. MISCELLANEOUS.--New York City Street Cars.                  7460

    Petroleum Wells.                                                7462

       *       *       *       *       *

PATENTS.

In connection with the =Scientific American=, Messrs. MUNN & CO.
are Solicitors of American and Foreign Patents, have had 39 years'
experience, and now have the largest establishment in the world.
Patents are obtained on the best terms.

A special notice is made in the =Scientific American= of all Inventions
patented through this Agency, with the name and residence of the
Patentee. By the immense circulation thus given, public attention is
directed to the merits of the new patent, and sales or introduction
often easily effected.

Any person who has made a new discovery or invention can ascertain,
free of charge, whether a patent can probably be obtained, by writing
to MUNN & CO.

We also send free our Hand Book about the Patent Laws, Patents,
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  +MUNN & CO.. 361 Broadway, New York.+
  Branch Office, cor. F and 7th Sts., Washington, D. C.


[Transcriber's Note:

Inconsistent spelling and hyphenation are as in the original.]





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