JF Ptak Science Books Post #74
I was drawn (like a moth to a ...) to these images that appeared in the journal Popular Science (New York), 1874, in an article by W.F. Barrett entitled “Sensitive Flames”. Actually I was more drawn to the title than the images, trying to conjure the differences between the other sorts of vaguely ethereal antiquarian flames that I imagined I was familiar with: quiet flames, singing flames, and the present sensitive flames. More or less “discovered” in 1857 by Joseph Le Conte (and then hammered in close comforting years soon after by Govi, Tyndall, Barry and Geyer), sensitive flames were noticed because they reacted to acoustic variations. These gas flames changed their shape according to the sorts of sounds and music that they were subjected to. (There are other factors involved here too of course, like the amount of gas used and the way in which the gas is released and so on—basically though they were the subject of change depending of their sensitivity to different sounds.)
Sensitive flames fall into a special category of reactive agents like Kundt’s dust figures and Cholodni’s watery acoustic images (and maybe even the wonderful dances of Brown's dust particles and Einstein's Brownian motions—unexpected, interesting and arresting images to watch produced by sound in an unexpected medium).
Early notices on the subject of “sensitive flames” appearing in the London-based journal Nature:
(1) Letters to Editor, Nature (03 December 1874)
Sounding and Sensitive Flames by A. S. HERSCHEL (Abstract)
IN a letter which I have just received from Dr. A. K. Irvine, of Glasgow, my
attention is drawn to a short abstract of some of his experiments with Barry's
sensitive flame, which appeared in the English Mechanic of Dec. 15, 1871, a few
months previously to the appearance in the Journal of the Franklin Institute, and in
the American Journal of Science, of the description, referred to briefly in my last
letter (NATURE, vol. xi. pp. 6 to 8), of Mr. Geyer's researches on the acoustic
properties of the same flame, some particulars of which Dr. Irvine appears also to
have noticed independently. The few lines in which his observations are recorded
corroborate so fully the character and mode of action of the flame as now pretty
perfectly established, that a short extract from them will scarcely be without
interest, from the satisfactory support which it offers to the accounts and
explanations that other investigators of this flame have elsewhere given ii graphic
terms of its appearance.
(2) Letters to Editor, Nature 11, 45-47 19 November 1874) Sounding and Sensitive Flames, II
(Abstract)
ANOTHER example of a highly sensitive flame was recently described to me which seems to show that air-currents flowing through gauze at a proper speed are sensitive
without the intervention or simultaneous superaddition of a flame. A special kind of Bunsen burner was made with a spiral mixing tube coiled in an inverted cup, at the
centre of which is a small chamber covered with wire-gauze at the foot of a short
tube or flame-pipe. The gas is admitted by a single jet passing through a cap of
wire-gauze covering the conical opening of the spiral tube, the object of this cap
of gauze being to distribute the air in its approach, and to protect the gas-jet
from ignition. The gas-flame burns with a small bright green cone, surmounted by a
larger envelope of pale reddish flame, and it is intensely hot. The green cone
indicates combustion of the most complete explosive mixture of air and coal-gas, and
when the burner is properly adjusted it can only burn on the top of the flame-tube,
where it finds the additional required supply of oxygen; but it descends to the
wire-gauze at the foot of the tube if the air-supply exceeds, or the gas supply
falls short of the right proportion. In some of these burners the slightest noise of
the kind that commonly affects sensitive flames causes the cone of green flame to
retreat into the tube and settle on the wire-gauze at its foot, whence it rises
again immediately to the top of the tube, when the sound ceases. The explanation
seems to be that the air-current entering the mixing-tube through the outer gauze
cap is in a sensitive condition, and that when thrown into disturbance by the
external sounds, it is more quickly seized and is drawn into the mixing tube more
rapidly by the gas-jet than when it is flowing over the jet in a tranquil state. The
inventor of these burners, Mr. Wallace, assures me that some of them exhibit the
most sensitive of sensitive flames, and that he has more than once thought of
sending one of them as a most singularly effective illustration of such flames to
Prof. Tyndall.
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