SOUND AND MUSIC 83 



surfaces, they are reflected again and again, and die away 

 in sweetest cadences. Curved roofs reflect sounds, and 

 sometimes concentrate them at points. Sound is also 

 refracted even as light. 



Velocity of sound. Its velocity passing through any 

 medium depends on the elasticity in relation to the 

 density, and when these are known the velocity is easily 

 determined, and always corresponds with the results 

 obtained by experiment. Density depends on tempera- 

 ture, and therefore its increase or decrease affects the 

 speed of transmission. In gases the velocity is least. 

 In air at Centigrade it is 1090 feet per second ; at 5, 

 1109 ; at 26-6, 1140. The increase is very nearly 2 feet 

 for every degree of temperature. The temperature may 

 be deduced from the velocity of sound. So perfect is 

 the observance of law in all material particles, so inti- 

 mately are their various characteristics connected, that 

 one may be employed to determine the other. All their 

 properties and potencies are measured. The velocity 

 in oxygen at C. is 1040 feet per second; in hy- 

 drogen, 4164 feet; in carbonic oxide, 1107 feet; in car- 

 bon dioxide, 858 feet. Each gas has at the same tempera- 

 ture the same measured relationship of elasticity to 

 density, and the same velocity with which it transmits 

 sound. In liquids the velocity is greater than in gases. 

 In river water, as in the Seine, at 15 C. it is 4174 feet 

 per second ; at 60 it is 5657. A salt dissolved in water 

 increases its elasticity in relation to its density, and so 

 makes the velocity greater. In a solution of common 

 salt at 18 it is 5130; of chloride of calcium, 6493. 

 In solids the elasticity in relation to the density is much 

 greater than in liquids, and therefore the transmission of 

 sound is much more rapid. In iron it is 16,822 feet per 

 second ; in copper, 11,666 ; in platinum, 8815 ; in silver, 



