EXPERIMENTAL INVESTIGATIONS 

 CONCERNING HEAT 



SECTION I. Short Account of a new Experiment on Heat. 



I HAVE lately made a new experiment, the result 

 of which appears to me sufficiently interesting to 

 deserve the attention of the Class. 



Having found, by experiments often repeated, that 

 metallic bodies, exposed in the free air of a large apart- 

 ment, are much more speedily heated and cooled when 

 their surfaces have been blackened (over the flame of a 

 candle, for example) than when they are clean and pol- 

 ished, I was curious to know whether the same phe- 

 nomena would take place when, instead of exposing 

 these bodies in the open air, they should be placed in 

 close metallic vessels, surrounded by a certain thickness 

 of included air, and these vessels should be then plunged 

 in a large mass of hot or cold water. In order to clear 

 up this important point, I made the following experi- 

 ment : 



A cylindrical vessel of brass, three inches in diame- 

 ter and four inches long, was enclosed in another larger 

 cylindrical vessel, in the centre of which it was sus- 

 pended by its neck, so as to touch it in no other part, 

 leaving on all sides an interval of one inch between the 

 vessels. 



The external vessel, as well as the smaller one in- 

 cluded within it, is made of thin sheets of brass; its 



