EDISON'S ACOUSTIC INVENTIONS. 



141 



A downward movement lets the chamber communicate with the 

 outlet H, an upward movement with the outlet G. The compressed 

 air enters at A, and fills the chamber, which, in its normal position, has 

 no outlet. Every downward vibration of the diaphragm will thus con- 



FiG. 34. 



dense the air in the pipe C, at the same time allowing the air in S to 

 escape via F. An upward movement condenses the air in C, but 

 opens I. 



The third and last part is shown in section in Fig. 35. It consists 

 of a cylinder and piston, jP, like that employed in an ordinary engine. 



Fro. 35. 



The piston-rod is attached to the centre of a large diaphragm, D. The 

 pipes C and B are continuations of those designated in Fig. 34 by the 

 same letters. The pipe C communicates with one chamber of the cylin- 

 der, and B with the other. The piston, moving under the influence of 

 the compressed air, moves also the diaphragm, its vibrations being, in 

 number and duration, identical with those of the dia2-)hragm in the 

 mouth-piece. 



