W. W. Jacques— Velocity of very Loud Sounds. 117 
densed portion of the wave is small compared with the density 
of the undisturbed air, the velocity should be independent both 
of the intensity and the pitch. 
1en, however, we come to the consideration of a loud and 
sharp shock or explosion, in which the disturbances are very 
violent and abrupt, we cannot be at all sure that the changes of 
density are negligibly small, and hence that the velocity of 
sound for such cases would be a constant. 
So little is known of the conditions in the case of the forma- 
tion and propagation of sound from a center of explosion, and 
the mathematical considerations of such conditions as we ma 
errors are due to the character of the sound or to other causes. 
The very short interval between the flash and the — of 
a stroke of lightning, even when it takes place at a considerable 
The following paper contains an account of some automatic 
measurements of the velocity of sound in the immediate 
vicinity of a cannon. The results show that the velocity near 
acannon is considerably different from that at a distance and 
point out a considerable error that has been introduced into the 
most important measurement of this quantity. : 
The experiments were made at the United States Arsenal in 
Watertown, Mass. 
The method used was an automatic measurement of the 
velocity at different distances, varying from ten to one hundred 
and ten feet, from the mouth of the cannon, by means of a 
Series of membranest electrically connected with a chronogr aph. 
In the midst of a large level field was placed a six-pound 
brass field piece. In the rear of this, at distances of 10, 30, 50, 
* Earnsha i ; ‘ Regnault's Memoirs. 
t Rognault u aca ideation sig unlike dest in his water-pipe experiments. 
