TN NA TURAL PHIL OSOPHY. ' 3 3 



Because it takes time for the sound-wave to pass down the 

 column, and hence those in the rear do not hear the music as 

 soon as those in front. 



2. Three minutes elapse between the flash and the report of a 

 thunderbolt : how far distant is it ? 



If the air is at the freezing point, the, distance is 

 1090 ft. x 60 x 3 = 196,200 ft. 



3. Five seconds expire between the flash and report of a gun : 

 what is the distance ? 



1090ft.x5 = 5450ft 



4. Suppose a speaking-tube should connect two villages 10 

 miles apart. How long would it take a sound to pass that 

 distance ? 



52,800 ft. -f- 1090 ft. = 48.4 (sec.) 



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

 the face of a cliff in 4 seconds. How far was it? 



1090 ft. x a = 2180 ft. 



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

 and woman ? 



It may be a difference in the length of the vocal chords, or 

 in the power of lengthening and shortening them; but it is not 

 yet fully understood. The difference between a bass and 

 tenor, as between a contralto and soprano voice, is probably 

 that of quality only, like that between different kinds of musical 

 instruments. 



7. What is the number of vibrations per second necessary to 

 produce the fifth tone of the scale of C ? 



(p. 176.) C t = 128 vibrations. G of that scale = 192 vibrations per second. 



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

 the temperature is zero ? 



1090 ft. 32 ft. =1058 ft, 1058 ft. -t- 192=5 ft. 6 -I- in. (the length of each vibration). 



9. What is the number of vibrations in the fourth fane above 

 middle C (CJ ? 



f^n 



C 8 = 256 vibrations . f ii _ (the proport i onate no . f or t h e 5th of tho scale). 



256 x = 384 (the number of vibrations per second). 



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