Sound. 373 



mediums. In air sound travels about 1,090 feet per second, in water 

 4,768 feet, in iron (at 68 F.) 16.822 feet, &c. 



The ratio of the vibrations which constitute our musical scale are as 

 follows : 



cdefgabc 

 1 A ft - t * s. 15. 9 or 



843238 



24 : 27 : 30 : 32 : 36 : 40 : 45 : 48 



Table Showing Number of Vibrations per second for each letter: 



It is evident that the length of the wave or vibration must vary with 

 the pitch in the same medium, and vary with the medium for the same 

 pitch. Sounds of every pitch travel at the same rate per second in the 

 same medium. The length of the wave of C, at the beginning of the 

 great octave, found by dividing 1090 feet by 132 is, in air, 8 feet 3 

 inches. In water it is 36 feet and one-tenth, in iron 127 and ^ feet. 

 For the C in the next octave above, these lengths are to be halved, and 

 are for air 4-J feet, for water 18^. feet, for iron 63^ feet, &c. In all 

 cases the vibration consists of the movement endwise of radii or spokes 

 of the elastic substance, which is the medium of conveyance. These 

 spokes are of the length of the wave. Starting at the point where the 

 blow first originates the sound, which we may call the center of a globe, 

 imagine these elastic spokes or rays to diverge in every direction, each 

 one having a length of 4-J feet. Surrounding this globe of spokes im- 

 agine another one consisting of four times as many spokes of the same 

 length, all pointing to the common center. Outside of this is to be 

 conceived another with nine times as many spokes. In short, add an 

 indefinite number of these spheres, numbering them from the center 1, 

 2, 3, 4, &c. The number of spokes contained in each one will be the 



