HISTORr of the SO'CIETT. 29 



This rule feems to be no other than that which regutates the 

 extrication of latent heat, when bodies pafs from a fluid to a 

 folid ftate, though this cafe is fomewhat more complicated than 

 xifual, and attended with circumftances that are yet but imper- 

 fetflly underftood. it mud therefore be confidered, whether 

 the fources of latent heat in the bodies, here combined, .be fuch 

 as we can reafonably fuppofe adetjuate to th^ effcCi produced. 



First, then, we have the latent heat of the fulphur, when it 

 is limply in its melted ftate ; it has then an aqueous or perfe(5l 

 fluidity, to which the quantity of its latent heat neceflarily cor- 

 refponds. But this is not precifely the ftate in which the ful- 

 phur combines with the metal ; for before that happens, and 

 while the fenfible heat increafes, the fulphur becomes vifcid, 

 and lofes its petfecfl fluidity. We have nothing with which we 

 can compare this phenomenon, or by which we can eftimate 

 the latent heat now contained in the fulphur. There is how- 

 . ever reafon to think, that this heat is of the fpecies which Dr 

 HuTTON, in his Diflertations on fubje<fl6 in Natural Philofophy, 

 diftinguifhes by the name of the latent heatofduSiility. The reafon 

 for this fuppofition is, that when the fulphur, in its vifcid ftate, 

 is plunged into cold water, it does not concrete into its ufual, 

 hard, friable, and cryftallized ftrudlure, but is changed, into a 

 tranfparent dudlile mafs. This ftate it feems to owe to the la- 

 tent heat contained in it; for after fome hours expofure to cold, 

 it gradually lofes its dudlility, and undergoes another change 

 of ftru(flure, fo as to refume its ordinary appearance, as if it 

 had been concreted and cryftallized from the ftate of fimple 

 fluidity. 



But the fulphur alio emits another Ipecies of heat, on its com- 

 bination with the metalUc fubftance. This is what may be 

 called the conftitutional heat of a body, or that by which its 

 volunje is preferved in oppofition to any force endeavouring to 



dixninilh 



