418 ECHO. 



Q. Why do very LARGE buildings (as cathe- 

 drals), often REVERBERATE the voice of the speaker ? 



A. Because the walls are so far off 

 from the speaker, that the echo does not 

 get back in time to blend with the original 

 sound; and, therefore, each is heard 

 separately. 



Q. Why do SOME echoes repeat only ONE 

 syllable ? 



A. The further the echoing body is 

 distant, the more sound it will reflect. 

 If, therefore, the echoing body be near, 

 it will repeat but one syllable. 



Q. Why does an ECHO sometimes repeat TWO 

 or more syllables ? 



A. Because the echoing body is far 

 off; and, therefore, there is time for one 

 reflection to pass away before another 

 reaches the ear. 



Q. Why do WINDOWS RATTLE when CARTS 

 pass by a house ? 



A. 1 st Glass is sonorous ; and the 

 air communicates its vibrations to the 

 glass, which echoes the same sound : and 



2ndly The window-frame is shaken 

 by the sound-waves impinging against the 

 window, and contributes to the noise. 



