PHYSICS NINETEENTH CENT. SOUND. 



535 



much of his attention. Many of his valuable papers on these subjects 

 were published in the "Memoirs" of the Academy of Sciences between 

 the years 1700 and 1714. 



The theoretical velocity of sound in various media was determined 

 by Newton. An interesting experimental investigation was that in 

 which COLLADON and STURM in 1826 determined the velocity of 

 sound in water. The experiments were conducted in the Lake of 

 Geneva. A bell was struck under water at the same instant that a 

 little gunpowder was fired, and the observer at a distance seeing the 



FIG. 249. 



flash, for the experiments were made at night, counted the number 

 of seconds which elapsed before he heard the stroke on the bell. 

 The arrangement of the apparatus is shown in Fig. 249, where c is 

 the bell, M the hammer by which it is struck, moved by means of a 

 lever. The same movement of the lever which causes the hammer 

 to strike the bell brings the lighted match M to the gunpowder at p, 

 which is thus fired at the very instant of the stroke. The distant 

 observer applies his ear to an ear-trumpet at o, the expanded end of 

 which, T, is submerged, and collects the sound. The velocity of sound 

 in water as given by these experiments is 4,708 feet per second. 

 The vibrations of a stretched cord can be followed by the eye when 



FIG. 250. 



they do not exceed about twelve per second. More rapid vibrations 

 give the appearance of a spindle-shaped nebulosity, as suggested by 

 the diagram Fig. 250, which -represents a cord vibrating as a whole. 



