Intelligence and Miscellaneous Articles. 219 



ON THE VELOCITY OF VERT LOUD SOUNDS. BT WILLIAM W. 

 JACQUES, FELLOW OF THE JOHNS HOPKINS UNIVERSITY. 



It is very well known that the Telocity of a musical sound is, 

 within very wide limits, sensibly independent of its intensity 

 and of its pitch. The experimental proof of this is that a piece 

 of music, played by a military band at a considerable distance, 

 comes to the ear of the observer with its harmony entirely un- 

 disturbed. 



A consideration of the theory of the propagation of a musical 

 sound, too, shows that for sounds such as we ordinarily hear, in 

 which the change of density from the rarefied to the condensed 

 portion of the wave is small compared with the density of the 

 undisturbed air, the Telocity should be independent both of the 

 intensity and the pitch. 



When, however, we come to the consideration of a loud and 

 sharp shock or explosion, in which the disturbances are Tery vio- 

 lent and abrupt, we cannot be at all sure that the changes of 

 density are negligibly small, and hence that the Telocity of sound 

 for such cases woidd be a constant. 



So little is known of the conditions in the case of the formation 

 and propagation of sound from a centre of explosion, and the 

 mathematical considerations of such conditions as we may presume 

 are so difficult, that we must look almost entirely to experiment 

 for our knowledge of the propagation of very loud sounds. But 

 our experimental eTidence on this point is Tery limited. Xearly 

 all of the experiments that haTe been made upon the Telocity of 

 sound haTe been made with cannon, and haTe not agreed re- 

 markably well with each other t nor haTe the thermodynamic quan- 

 tities calculated from them, on the supposition that the Telocity 

 is identical with that of a musical sound, agreed Tery well with 

 the values of the same quantities determined by other methods. 

 But we cannot say whether these errors are due to the character 

 of the sound or to other causes. 



The very short interval between the flash and the report of a 

 stroke of lightning, even when it takes place at a considerable 

 distance, has been instanced* as a proof of the greater velocity of 

 very loud sounds ; but, so far as the writer is aware, this has not 

 yet been reduced to experiment. 



The experiments o£ Regnault f in water-pipes showed that the 

 velocity of a pistol-report became slightly less each time that it 

 was reflected along the pipe ; but the change was very small, and 

 its cause is doubtful. 



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 a cannon is 

 considerably different from that at a distance, and point out a 



* Eamshaw, Phil. Mag. 1860. t Regnault's l Memoirs.' 



