206 Proceedings of Indiana Academy of Science. 
It will be noted that Regnault obtains a velocity of 334.2 m./sec. near 
the source in a pipe 110 cm. in diameter, and that the velocity at 2,000 m. 
from the source has decreased to 330.5 m./sec. A pipe 10.8 cm. in diam- 
eter gave a smaller initial velocity and a much more rapid variation of 
that velocity with distance from the source. (The curve indicates, too, 
a much greater total variation in the case of a small pipe.) Regnault 
concluded that: (1) The velocity of sound in pipes varies inversely with 
the diameter; (2) the velocity decreases as the distance from the source 
increases; (3) the limiting velocity is the same for all sources. 
Rink objected to Regnault’s deductions and explained the greater 
initial velocity as due to the fact that, during the first few coursings, 
the sound wave would be traveling in air moving bodily as the result 
of the explosion which produced the wave. 
TABLE I. 
Rink’s Analysis of Regnauit’s Experiments. 
| 
| Charge Speed in em. per Sec. of Each Passage of Sound Along Pipe Mean 
No.of | of Gun 110 em. Diameter. Speed for 
Experi- | Powder — Given 
ment. | in Pistol | 3rd | 4th 5th 6th | — 7th | 8th Charge of 
inGms. | Passage | Passage Passage | Passage | Passage | Passage Powder 
1 0.5 330.02 330.29 330.15 | 330.21 330.11 330.13 330.152 
2 1.0 330.36 330.59 330.57 | 330.61 | 330.44 | 330.42 330.498 
3 1.5 330.29 330.57 330.54 330.47 330.47 | 330.53 330.433 
4 2 330.60 | 330.51 330.84 | 330.44 | 330.44 330.30 330.513 
5 1 330.04 330.26 330.26 | 330.23 | 330.15 230.22 330.193 
6 | 1 330.36 330.37 330.50 | 330.67 330.55 | 330.50 330.492 
Mean Speed for each | 
Passage..... --.-| 330.278 330.428 339.477 330.452 330.360 | 330.330 | 
| | 
The above table gives the results of Rink’s analysis of Regnault’s 
experiments and appears to confirm Rink’s contention that the true 
velocity of sound in a given pipe is constant, the result for a pipe 110 cm. 
in diameter being 330.5 m./sec. For a pipe 7 cm. in diameter LeRoux, 
using Regnault’s methods, obtained a velocity of 330.66 m./sec. 
Regnault, in 1865, by the reciprocal firing of guns, the explosion 
breaking an electrical circuit at the source, the wave—by moving a 
membrane—breaking another circuit at a distant point, both circuits 
making stylus records on the same chronograph, obtained velocities of 
331.87 m./sec. and 330.7 m./sec. at distances respectively of 1,280 m. 
and 2,445 m. from the source. In all of Regnault’s experiments effdrts 
were made to determine and to correct for the time lag of the recording 
apparatus. The error due to this cause can not be entirely eliminated 
for two reasons. In the first place the lag depends on the intensity of 
the wave and is therefore a function of the distance from the source, 
