OF THE VIBRATIONS OF AN INVARIABLE PENDULUM. 



223 



Whence it appears as the result of this experiment, that a difference of 9.54 

 vibrations per diem corresponds to a difference of atmospheric pressure of 

 27.459 inches of mercuiy at 32° ; the temperature of the air of full pressure 

 being 35°.89, and that of the rarefied air 36°.5. 



The trifling leakage of the apparatus in this and the following experiment 

 was attributed, and as it was afterwards proved justly, to the severity of the 

 weather, which hardened the pomatum so that it did not secure the joinings of 

 the glasses so well as usual. 



Exp. IV. — January 1 7th and 18th. Clock gaining 4" 14\38. 



The air was then withdrawn, and the following observations made ; the 

 valves of the pump requiring repair, the gauge could not be I'educed lower 

 than 3 inches. 



The air was then admitted, and the following observations made the next 

 morning. 



