EAR TRUMPETS, ETC. 415 



(raised by the action of the sun's rays) 

 cease as the evening advances ; and 



2ndly Night is more still from the 

 suspension of business, and the cessation 

 of the hum of men. 



Q. How should PARTITION WALLS be made to 

 PREVENT the voices in adjoining rooms from being 



HEARD ? 



A. The space between the laths (or 

 canvass) should be filled with shavings or 

 saw-dust; and then no sound would ever 

 pass from one room to another. 



Q. Why would SHAVINGS or saw-dust PRE- 

 VENT the transmission of sound from room to room ? 



A. Because there would be several 

 different media for the sound to pass 

 through: 1st the air; 2ndly the laths 

 and paper ; Srdly the saw-dust or sha- 

 vings ; 4thly the air again : and every 

 variety diminishes the strength of the 

 sound-waves. 



Q. Why can DEAF people hear through an 



EAR TRUMPET ? 



A. The ear trumpet restrains the 

 spread of the voice, and limits the 

 diameter of the sound-waves; in con- 



