SOUND. 119 



MRS. F. 



It is formed of a wooden or tin tube with a small piston at 

 each end. By pushing in one piston, the air in the tube con- 

 veys the effect to the piston at the other end, which strikes 

 against a bell; this piston being, as it were, the clapper on 

 the outside of the bell. 



FREDERICK. 



How ingenious! 



MRS. F. 



The next point to be considered is the phenomenon of 

 reflected sounds or echoes, some of which are hardly credible. 

 Sound is reflected in the same manner as light. 



ESTHER. 



The angle of reflection being equal to the angle of inci- 

 dence. 



MRS. F. 



Or to speak in less philosophical, but perhaps more intelli- 

 gible terms, the angle by which light or sound is reflected 

 back from an even surface, is exactly equal to that by which 

 it is received. 



- HENRIETTA. 



I have heard of an echo which repeats sixty times. 



ESTHER. 



That is at the Marquis Simonetta's villa near Milan, and 

 has been described by Addison. 



MRS. F. 



Bat in some travels in Sicily, which I was reading yester- 

 day, I met with a curious circumstance, which you shall hear. 

 " In the cathedral of Gergenti. in Sicily (the ancient Agrigen- 

 tum), the slightest whisper is borne with perfect distinctness 

 from the great western door to the cornice behind the high altar, 

 a distance of 250 feet. By a most unlucky coincidence, the 

 precise point of divergence near the door, was chosen for the 



