IN POPULAR PHYSICS. 39 



5. The report of a pistol-shot was returned to the ear 

 from the face of a cliff in 4: seconds. Hoiv far was it ? 



.1,090ft. x2 = 2, 180 ft. 



6*. What is the cause of the difference in the voice of 

 man and wom,an ? 



Probably the difference depends largely on the thickness 

 and length of the vocal chords. The difference between a bass 

 and a tenor, a contralto and a soprano, depends largely also on 

 quality, just as the sound of the flute and violin on the same 

 note is recognizably different. 



7. What is the number of vibrations per second neces- 

 sary to produce the fifth tone of the scale of C s ? 



C 3 = 256 vibrations. 

 256 x f = 384. 



8. Wliat is the length of each sound-wave in that tone 

 ivhen the temperature is zero F. ? 



1,090 ft. -32 ft. = 1,058 ft. 1,058 -f- 384 = 2 ft. 9 in. (the length 

 of each wave). 



9. What is the number of vibrations in the fourth tone 

 above C 3 ? 



C 2 = 128 vibrations. 

 128 xf =192. 



lO.Ifa meteor were to explode at a height of 60 miles, 

 ivould it be possible for its sound to be heard at sea-level ? 



No. At such a height the atmosphere would be more rare 

 than in the best vacuum over produced by human means. The 

 explosion would produce a sound far too faint to be audible. 



11. A stone is let fall into a well, and in four seconds is 

 heard to strike the bottom ; hoiv deep is the ^vell ? 



Disregarding the minute interval required for the transmis- 

 sion of the sound, 



S = P = 16 x 4 2 = 256 feet. 



