OF THE VIBRATIONS OF AN INVARIABLE PENDULUM. 



225 



The air was then re-admitted, and the following observations made. 



The vibrations in this experiment were as follows : 



January 30. Previous to the vibration in") o^on= r^^ t> nr^ a^. ■ x. 



the rirefied medium | 86305.97 ; Barom. 29.474 mches. 



Januarys!. Subsequent to the vibration! „„„„. ^„ „ o^/ir, 



in the rarefied medium | 8630o. 69 ; Barom. 30.051 



Mean 



86305.83 ; Barom. 29.762 



The vibrations in a rarefied medium reduced "lo^oi^^o, /-. r^ ^r^ ■ i 



to the same temperature as those in air J^f^^ffi' ^^^S^ ^^ ^^^hes. 



Whence there appears as the result of this experiment, a difference of 10.38 

 vibrations per diem, corresponding to a difference of atmospheric pressure of 

 29.109 inches of mercury at 32°; the temperature of the air of full pressure 

 being 36°.4 ; and that of the rarefied air, 36°.52. 



MDCCCXXIX. 2 G 



