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XVI. On the Communication of Vibration from a Vibrating Body to a surrounding Gas. 
By G. G. Stokes, M.A., D.C.L., Sec. B.S., Fellow of Pembroke College , and Lucasian 
Professor of Mathematics in the University of Cambridge. 
Received June 18, — Read June 18, 1868. 
In the first volume of the Transactions of the Cambridge Philosophical Society is a 
short paper by Professor John Leslie, “ On Sounds excited in Hydrogen Gas,” in which 
the author mentions some remarkable experiments indicating the singular incapacity of 
hydrogen for becoming the vehicle of the transmission of sound when a bell is struck in 
that gas, either pure or mixed with air. With reference to the most striking of his 
experiments the author observes (p. 267), “ The most remarkable fact is, that the 
admixture of hydrogen gas with atmospheric air has a predominant influence in blunting 
or stifling sound. If one half of the volume of atmospheric air be extracted [from the 
receiver of the air-pump], and hydrogen gas be admitted to fill the vacant space, the 
sound will now become scarcely audible.” 
No definite explanation of the results is given, but with reference to the feebleness 
of sound in hydrogen the author observes, “ These facts, I think, depend partly on the 
tenuity of hydrogen gas, and partly on the rapidity with which the pulsations of sound 
are conveyed through this very elastic medium ; ” and he states that, according to his 
view, he “ should expect the intensity of sound to be diminished 100 times, or in the 
compound ratio of its tenuity and of the square of the velocity with which it conveys 
the vibratory impressions.” With reference to the effect of the admixture of hydrogen 
with air he says, “ When hydrogen gas is mixed with common air, it probably does not 
intimately combine, but dissipates the pulsatory impressions before the sound is vigo- 
rously formed.” 
In referring to Leslie’s experiment in which a half-exhausted receiver is filled up with 
hydrogen, Sir John Herschel suggests a possible explanation founded on Dalton’s 
hypothesis that every gas acts as a vacuum towards every other *. According to this 
view there is a constant tendency for sound-waves to be propagated with different velo- 
cities in the air and hydrogen of which the mixture consists, but this tendency is con- 
stantly checked by the resistance which one gas opposes to the passage of another, 
calling into play something analogous to internal friction, whereby the sound-vibration 
though at first produced is rapidly stifled. Air itself indeed is a mixture ; but the 
velocities of propagation of sound in nitrogen and oxygen are so nearly equal that the 
effect is supposed not to be sensible in this case. 
* Encyclopaedia Metropolitana, vol. iv. Art. Sound, § 108. 
3 R 
MDCCCLXVIII. 
