Copyright
D. S. (David Samuel) Margoliouth.

The Popular science monthly (Volume 19) online

. (page 5 of 110)
Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 5 of 110)
Font size
QR-code for this ebook


pp^'



ACTIOX OF RADIANT HEAT. 35



reasoned, would produce faint sounds, while liighly atliermanous
bodies would produce loud sounds ; the strength of the sound being,
in a sense, a measure of the absorption. The first experiment made,
with a view of testing this idea, was executed in the presence of Mr.
Graham Bell ; * and the result was in exact accordance with what I had
foreseen.

The inquiry has been recently extended so as to embrace most of
the gases and vapors employed in my former researches. My first
source of rays was a Siemens lamp connected with a dynamo-machine,
worked. by a gas-engine. A glass lens was used to concentrate the
rays, and afterward two lenses. By the first the rays were rendered
parallel, while the second caused them to converge to a point about
seven inches distant from the lens. A circle of sheet-zinc provided first
with radial slits and afterward with teeth and interspaces, cut through
it, was mounted vertically on a whirling table, and caused to rotate
rapidly across the beam near the focus. The passage of the slits pro-
duced the desired intormittence, f while a flask containing the gas or
vapor to be examined received the shocks of the beam immediately
behind the rotating disk. From the flask a tube of India-rubber, end-
ing in a tapering one of ivory or boxwood, led to the ear, which was
thus rendered keenly sensitive to any sound generated within the flask.
Compared with the beautiful apparatus of Mr. Graham Bell, the ar-
rangement here described is rude ; it is, however, very effective.

With this arrangement the number of' sounding gases and vapors
was rapidly increased. But I was soon made aware that the glass
lenses withdrew from the beam its most effectual rays. The silvered
mirrors employed in my previous researches were therefore invoked ;
and with them, acting sometimes singly and sometimes as conjugate
mirrors, the curious and striking results which I have now the honor
to submit to the Society were obtained.

Sulphuric ether, formic ether, and acetic ether, being placed in
Iiulbous flasks,! their vapors were soon diffused in the air above the
liquid. On placing these flasks, whose bottoms only were covered by
the liquid, behind the rotating disk, so that the intermittent beam

• On the 29th November : see " Journal of the Society of Telegraph Engineers,"
December 8, 1880.

t Wlicn the disk rotates, the individual slits disappear, fonning a hazy zone through
which objects are visible. Throwing by the clean hand, or better still by white paper,
the beam back upon the disk, it appears to stand still, the slits forming so many dark
rectangles. The reason is obvious, but the experiment is a very beautiful one.

I may add that when I stand with open eyes in the flashing beam, at a definite ve-
locity of recurrence, subjective colors of" extraordinary gorgcousness are produced. With
slower or quicker rates of rotation the colors disappear. Tiic flashes also produce a
-riJdiness sometimes intense enough to cause me to grasp the table to keep myself erect.

X I have emplo3-ed flasks measuring from eight inches to three-fourths of an inch in
diameter. The smallest flask, which had a stem with a bore of about one eighth of an inch
in diameter, yielded better effects than the largest. Flasks from two to three inches in
diameter yield good results. Ordinary test-tubes also answer welL



36 THE POPULAR SCIENCE MONTHLY.

passed through the vapor, loud musical tones were in each case ob-
tained. These are known to be the most highly absorbent vapors
which my experiments revealed. Chloroform and bisulphide of carbon,
on the other hand, are known to be the least absorbent, the latter
standing near the head of diathermanous vapors. The sounds ex-
tracted from these two substances were usually weak and sometimes
barely audible, being more feeble with the bisulphide than with the
chloroform. With regard to the vapors of amylene, iodide of ethyl,
iodide of methyl and benzol, other things being equal, their power to
produce musical tones appeared to be accurately expressed by their
ability to absorb radiant heat.

It is the vapor, and not the liquid, that is effective in producing
the sounds. Taking, for example, the bottles in which my volatile
substances are habitually kept, I peimitted the intermittent beam to
impinge upon the liquid in each of them, Ko sound was in any case pro-
duced, while, the moment the vapor-laden space above an active liquid
was traversed by the beam, musical tones made themselves audible.

A rock-salt cell filled entirely with a volatile liquid, and subjected
to the intermittent beam, produced no sound. This cell was circular
and closed at the top. Once, while operating with a highly atherma-
nous substance, a distinct musical note was heard. On examining the
cell, however, a small bubble was found at its top. The bubble was
less than a quarter of an inch in diameter, but still sufficient to pro-
duce audible sounds. When the cell was completely filled, the sounds
disappeared.

It is hardly necessary to state that the pitch of the note obtained in
each case is determined by the velocity of rotation. It is the same as
that produced by blowing against the rotating disk and allowing its
slits to act like the perforations of a siren.

Thus, as regards vapors, prevision has been justified by experi-
ment. I now turn to gases, A small flask, after having been heated
in the spirit-lamp so as to detach all moisture from its sides, was care-
fully filled with dried air. Placed in the intermittent beam it yielded
a musical note, but so feeble as to be heard only with attention. Dry
oxygen and hydrogen behaved like dry air. This agrees with my
former experiments, which assigned a hardly sensible absorption to
these gases. When the dry air was displaced by carbonic acid, the
sound was far louder than that obtained from any of the elementary
gases. When the carbonic acid was displaced by nitrous oxide, the
sound was much more forcible still, and, when the nitrous oxide was
displaced by defiant gas, it gave birth to a musical note which, when
the beam was in good condition and the bulb M'ell chosen, seemed as
loud as that of an ordinary organ-pipe.* We have here the exact order

* With conjugate mirrors, the sounds with defiant gas are readily obtained at a dis-
tance of twenty yards from the lamp. I hope to be able to make a candle-flame effective
in these experiments.



ACTION OF RADIANT HEAT. 37

in which my former experiments proved these gases to stand as ab-
sorbers of radiant heat. The amount of the absorption and the inten-
sity of the sound go hand in hand.

A soap-bubble bloA\Ti with nitrous oxide, or olefiant gas, and exposed
to the intermittent beam, produced no sound, no matter how its size
might be varied. The pulses obviously expended themselves upon
the flexible envelope, which transferred them to the air outside.

But a film thus impressionable to impulses on its interior surface
must prove at least equally sensible to sonorous waves impinging on
it from without. Hence, I inferred, the eminent suitability of soap-
bubbles for sound-lenses. Placing a " sensitive flame " some feet dis-
tant from a small sounding reed, the pressure was so arranged that the
flame burned tranquilly. A bubble of nitrous oxide (specific gravity
1"52T) was then blown, and placed in front of the reed. The flame
immediately fell and roared, and continued agitated as long as the lens
remained in position. A pendulous motion could be imparted to the
l)ubble, so as to cause it to pass to and fro in front of the reed. The
'!ame responded, by alternately roaring and becoming tranquil, to
every swing of the bubble. Nitrous oxide is far better for this experi-
ment than carbonic acid, which speedily ruins its envelope.

The pressure was altered so as to throw the flame, when the reed
soimded, into violent agitation. A bubble blown with hydrogen
(specific gravity 0'069) being placed in front of the reed, the flame
was immediately stilled. The ear answers instead of the flame.

In 1859 I proved gaseous ammonia to be extremely impervious to
radiant heat. My interest in its deportment when subjected to this
novel test was therefore great. Placing a small quantity of liquid
ammonia in one of the flasks, and warming the liquid slightly, the
intermittent beam was sent through the space above the liquid. A
loud musical note was immediately produced. By the proper applica-
tion of heat to a liquid the sounds may be always intensified. The
ordinary temperature, however, suflices in all the cases thus far re-
ferred to. In this relation the vapor of water was that which inter-
ested me most, and, as I could not hope that at ordinary temperatures
it existed in sufiicient amount to produce audible tones, I heated a
small quantity of water in a flask almost up to its boiling-point.
Placed in the intermittent beam, I heard — I avow with delight — a
powerful musical sound produced by the aqueous vapor.

Small wreaths of haze, produced by the partial condensation of the
vapor in the upper and cooler air of the flask, were, however, visible
in this experiment ; and it Avas necessary to prove that this haze was
not the cause of the sound. The flask was, therefore, heated by a
spirit-flame beyond the temperature of boiling water. The closest
scrutiny by a condensed beam of light then revealed no trace of cloudi-
ness above the liquid. From the perfectly invisible vapor, however,
the musical sound issued, if anything, more forcible than before. I



38 THE POPULAR SCIENCE MONTHLY.

placed the flask in cold water until its temperature was reduced from
about 90° to 10° C, fully expecting that the sound would vanish at
this temperature ; but, notwithstanding the tenuity of the vapor, the
sound extracted from it was not only distinct but loud.

Three empty flasks, filled with ordinary air, were placed in a freez-
ing mixture for a quarter of an hour. On being rapidly transferred
to the intermittent beam, sounds much louder than those obtainable
from dry air were produced. Warming these flasks in the flame of a
spirit-lamp until all visible humidity had been removed, and afterward
urging dried air through them, on being placed in the intermittent
beam the sound in each case was found to have fallen almost to silence.
Sending, by means of a glass tube, a puff of breath from the lungs
into a dried flask, the power of emitting sound was immediately re-
stored. When, instead of breathing into a dry flask, the common air
of the laboratory was urged through it, the sounds became immediately
intensified. I was by no means prepared for the extraordinary deli-
cacy of this new method of testing the athermancy and diathermancy
of gases and vapors, and it can not be otherwise than satisfactory to
me to find that particular vapor, whose alleged deportment toward
radiant heat has been so strenuously denied, aflirming thus audibly its
true character.

After what has been stated regarding aqueous vapor, we are pre-
pared for the fact that an exceedingly small percentage of any highly
athermanous gas diffused in air suffices to exalt the sounds. An acci-
dental observation will illustrate this point. A flask was filled with
coal-gas, and held bottom upward in the intermittent beam. The
sounds produced were of a force corresponding to the known absorp-
tive energy of coal-gas. The flask was then placed upright, with its
mouth open upon a table, and permitted to remain there for nearly an
hour. On being restored to the beam, the sounds produced were far
louder than those which could be obtained from common air.*

Transferring a small flask or a test-tube from a cold place to the
intermittent beam, it is sometimes found to be practically silent for a
moment, after which the sounds become distinctly audible. This I
take to be due to the vaporization by the calorific beam of the thin
film of moisture adherent to the glass.

My previous experiments having satisfied me of the generality of
the rule that volatile liquids and their vapors absorb the same rays, I
thought it probable that the introduction of a thin layer of its liquid,
even in the case of a most energetic vapor, would detach the effective
rays, and thus quench the sounds. The experiment was made, and
the conclusion verified. A layer of water, formic ether, sulphuric
ether, or acetic ether, one eighth of an inch in thickness, rendered the
transmitted beam powerless to produce any musical sound. These

* The method here described is, I doubt not, applicable to the detection of extremely
small quantities of fire-damp in mines.



ACTION OF RADIANT HEAT. 39

liquids being transparent to light, the efficient rays which they inter-
cepted must have been those of obscure heat.

A layer of bisulphide of carbon, about ten times the thickness of
the transparent layers just referred to, and rendered opaque to light by
dissolved iodine, was interposed in the path of the intermittent beam.
It produced hardly any diminiition of the sounds of the more active
vapors — a further proof that it is the invisible heat-rays, to which the
solution of iodine is so eminently transparent, that are here effectual.

Converting one of the small flasks used in the foregoing experi-
ments into a thermometer-bulb, and filling it with various gases in
succession, it was found that Avith those gases which yielded a feeble
sound the displacement of a thermometric column associated with the
1)ulb was slow and feeble, while with those gases which yielded loud
sounds the displacement was prompt and forcible.

Since the handing in of the foregoing note, on the 3d of January,
the experiments have been pushed forward, augmented acquaintance
with the subject serving only to confirm my estimate of its interest
and importance. All the results described in my first note have been
obtained in a very energetic form with a battery of sixty Grove's
cells.

On the 4th of January I chose for my source of rays a powerful
lime-light, which, when suflicient care is taken to prevent the pitting
of the cylinder, works with admirable steadiness and without any
noise. I also changed my mirror for one of shorter focus, which per-
mitted a nearer approach to the source of rays. Tested with this new
reflector the stronger vapors rose remarkably in sounding power.

Improved manipulation was, I considered, sure to extract sounds
from rays of much more moderate intensity than those of the lime-
light. For this light, therefore, a common candle flame was substi-
tuted. Received and thrown back by the mirror, the radiant heat of
the candle produced audible tones in all the stronger vapors. Aban-
doning the mirror and bringing the candle close to the rotating disk,
its direct rays produced audible sounds. A red-hot coal, taken from
the fire and held close to the rotating disk, produced forcible sounds
in a flask at the other side. A red-hot poker, placed in the position
jireviously occupied by the coal, produced strong sounds. Maintain-
ing the flask in position behind the rotating disk, amusing alternations
of sound and silence accompanied the alternate introduction and re-
moval of the poker. The temperature of the iron was then lowered
till its heat just ceased to be visible. The intermittent invisible rays
l>roduccd audible sounds. The temperature was gradually lowered,
l)eing accompanied by a gradual and continuous diminution of the
sound. When it ceased to be audible the temperature of the poker
was found to be below that of boiling water.
As might be expected from the foregoing experiments, an incandes-



40 THE POPULAR SCIE^^CE MONTHLY.

cent platinum spiral, with or without the mirror, produced musical
sounds. When the battery power was reduced from ten cells to three,
the sounds, though enfeebled, were still distinct.

My neglect of aqueous vapor had led me for a time astray in 1859,
but before publishing my results I had discovered my error. On the
present occasion this omnipresent substance had also to be reckoned
with. Fourteen flasks of various sizes, with their bottoms covered
with a little sulphuric acid, were closed with ordinary corks and per-
mitted to remain in the laboratory from the 23d of December to the
4th of January. Tested on the latter day with the intermittent beam,
half of them emitted feeble sounds, but half were silent. The sounds
were undoubtedly due, not to dry air, but to traces of aqueous vapor.

An ordinary bottle, containing sulphuric acid for laboratory pur-
poses, being connected with the ear and placed in the intermittent
beam, emitted a faint but distinct musical sound. This bottle had
been opened two or three times during the day, its dryness being thus
vitiated by the mixture of a small quantity of common air. A second
similar bottle, in which sulphuric acid had stood undisturbed for some
days, was placed in the beam : the dry air above the liquid proved
absolutely silent.

On the evening of January 7th Professor Dewar handed me four
flasks treated in the following manner : Into one was poured a small
quantity of strong sulphuric acid ; into another a small quantity of
Nordhausen sulphuric acid ; in a third were placed some fragments
of fused chloride of calcium ; while the fourth contained a small
quantity of phosphoric anhydride. They were closed with well-fitting
India-rubber stoppers, and permitted to remain undisturbed through-
out the night. Tested after twelve hours, each of them emitted a
feeble sound, the flask last mentioned being the strongest. Tested
again six hours later, the sound had disappeared from three of the
flasks, that containing the phosphoric anhydride alone remaining
musical.

Breathing into a flask partially filled with sulphuric acid instantly
restores the sounding power, which continues for a considerable time.
The wetting of the interior surface of the flask with the sulphuric
acid always enfeebles and sometimes destroys the sound.

A bulb, less than a cubic inch in volume, and containing a little
water, lowered to the temperature of melting ice, produces very dis-
tinct sounds. "Warming the water in the flame of a spirit-lamp, the
sound becomes greatly augmented in strength. At the boiling tem-
perature the sound emitted by this small bulb * is of extraordinary
intensity.

These results are in accord with those obtained by me nearly nine-
teen years ago, both in reference to air and to aqueous vapor. They

* In such bulbs even bisulphide-of -carbon vapor may be so nursed as to produce
sounds of considerable strenath.



■Pr



ACTION OF RADIANT HEAT. 41



are in utter disaccord with those obtained by other experimenters,
who have ascribed a high absorption to air and none to aqueous vapor.

The action of aqueous vapor being thus revealed, the necessity of
thoroughly drying the flasks, when testing other substances, becomes
obvious. The following plan has been found effective : Each flask is
first heated in the flame of a spirit-lamp until every visible trace of
internal moisture has disappeared, and it is afterward raised to a tem-
perature of about 400° 0. While the flask is still hot, a glass tube is
introduced into it, and air, freed from carbonic acid by caustic potash
and from aqueous vapor by sulphuric acid, is urged through the flask
until it is cool. Connected with the ear-tube, and exposed immediately
to the intermittent beam, the attention of the ear, if I may use the
term, is converged upon the flask. When the experiment is carefully
made, dry air proves as incompetent to produce sound as to absorb
radiant heat.

In 1868 I determined the absorptions of a great number of liquids
whose vapors I did not examine. My experiments having amply
proved the parallelism of liquid and vaporous absorption, I held un-
doubtingly twelve years ago that the vapor of cyanide of ethyl and
of acetic acid would prove powerfully absorbent. This conclusion is
now easily tested. A small quantity of either of these substances,
placed in a bulb a cubic inch in volume, warmed and exposed to the
intermittent beam, emits a sound of extraordinary power.

I also tried to extract sounds from perfumes, which I had proved
in 18G1 to be absorbers of radiant heat. I limit myself here to the
vapors of patchouly and cassia, the former exercising a measured ab-
sorption of 30, and the latter an absorption of 109. Placed in dried
flasks, and slightly warmed, sounds were obtained from both these
substances, but the sound of cassia was much louder than that of
patchouly.

Many years ago I had proved tetrachloride of carbon to be highly
diathermanous. Its sounding power is as feeble as its absorbent
power.

In relation to colliery explosions, the deportment of marsh-gas was
of special interest. Professor Dewar was good enough to furnish me
with a pure sample of this gas. The sounds produced by it, when
exposed to the intermittent beam, were very powerful. Chloride of
methyl, a liquid which boils at the ordinary temperature of the air, was
poured into a small flask, and permitted to displace the air within it.
Exposed to the intermittent beam, its sound was similar in power to
that of marsh-gas. The specific gravity of marsh-gas being about
half that of air, it might be expected that the flask containing it, when
left open and erect, would soon get rid of its contents. This, however,
is not the case. After a considerable interval, the film of this gas
clinging to the interior surface of the flask was able to produce sounds
of great power.



42 THE POPULAR SCIENCE MONTHLY.

A small qiiantity of liquid bromine being poured into a well-dried
flask, the brown vapor rapidly difused itself in the air above the
liquid. Placed in the intermittent beam, a somewhat forcible sound
was produced. This might seem to militate against my fonner experi-
ments, which assigned a very low absorptive power to bromine vapor.
But my former experiments on this vapor were conducted with ob-
scure heat ; whereas, in the present instance, I had to deal with the
radiation from incandescent lime, whose heat is, in part, luminous.
Now, the color of the bromine vapor proves it to be an energetic ab-
sorber of the luminous rays ; and to them, when suddenly converted
into thermometric heat in the body of the vapor, I thought the sounds
might be due.

Between the flasks containing the bromine and the rotating disk, I
therefore placed an empty glass cell : the sounds continued. I then
filled the cell with transparant bisulphide of carbon : the sounds still
continued. For the transparent bisulphide I then substituted the same
liquid saturated with dissolved iodine. This solution cut off the light
while allowing the rays of heat free transmission : the sounds were
immediately stilled.

Iodine, vaporized by heat in a small flask, yielded a forcible sound,
which was not sensibly affected by the interposition of transparant
bisulphide of carbon, but which was completely quelled by the iodine
solution. It might indeed have been foreseen that the rays trans-
mitted by the iodine as a liquid would also be transmitted by its
vapor, and thus fail to be converted into sound.*

To complete the argument : While the flask containing the bro-
mine vapor was sounding in the intermittent beam, a strong solution
of alum was interposed between it and the rotating disk. There was
no sensible abatement of the sounds with either bromine or iodine
vapor.

In these experiments the rays from the lime-light were converged
to a point a little beyond the rotating disk. In the next experiment
they were rendered parallel by the mirror, and afterward rendered
convergent by a lens of ice. At the focus of the ice-lens the sounds
were extracted from both bromine and iodine vapoi*. Sounds were
also produced after the beam had been sent through the alum solution
and the ice-lens conjointly.

With a very rude arrangement I have been able to hear the sounds
of the more active vapors at a distance of one hundred feet from the
source of rays.

Several vapors other than those mentioned in this abstract have
been examined, and sounds obtained from all of them. The vapors
of all compound liquors will, I doubt not, be found sonorous in the
intermittent beam. And, as I question whether there is an absolutely

* I intentionally use this phraseology.



AX OTHER WORLD DOWX HERE. 43

diathermanous substance in nature, I think it probable tliat even the
vapors of elementary bodies, including the elementary gases, when
more strictly examined, will be found capable of producing sounds.



AXOTHER WORLD DOWX HERE.

Bv ^y. MATTLEU WILLIAMS.

WHAT a horrible place must this world appear when regarded ac-



Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 5 of 110)