on the Subject of Heat. 239 



and exposed at the same time to the air, in which they 

 were allowed to cool. The water contained in the glass 

 flask cooled twice as fast as that in the one made of 

 tinned iron, although the walls of the latter were much 

 thinner than those of the glass flask. This memoir 

 ends with some considerations on the comparison which 

 has been instituted between a warm body and a sponge 

 filled with water, and on the influence of radiation dur- 

 ing the warming and cooling of bodies. 



On the iyth Floreal (yth of May, 1804) I laid before 

 the Class my fifth memoir, in which I gave an account of 

 an entirely new series of experiments, which I had made 

 in Paris, on the manner in which heat is propagated in 

 a massive bar of metal, six inches long ana an. inch and 

 a half- in diameter. This bar was heated at one end 

 by boiling water, and cooled at the other end some- 

 times with a mixture of pounded ice and water, and 

 sometimes simply with water of the temperature of the 

 air. 



M. Biot, member of the Institute, made, at about the 

 same time with myself, several successive experiments 

 on the propagation of heat in metallic bars and other 

 solid bodies. He, however, used for this purpose bars 

 of a different length from mine, and higher tempera- 

 tures. Otherwise we obtained the same results from 

 our experiments. 



He hit upon the fortunate idea of employing similar 

 experiments for measuring very high degrees of tem- 

 perature ; such, for example, as is necessary in the 

 preparation of porcelain, or for melting metals not 

 readily fusible. 



As I was invited to prepare a condensed description 

 of my recent experiments on heat, to be read at the 



