1 3 4 V/byJme Fluids an permanently elaft'ic. [Book 1 1 . 



glafs : and as the diamond itfelf has been fubjected to 

 evaporation, it is not improbable that by a fufficirnt 

 quantity of heat every other mineral fubflance might 

 be fufed and volatilized. 



The vapour of water, and mod other fluids, requir- 

 ing a degree of heat above that of the atmofphere to 

 keep it in a volatile ftate, is eafily deprived of its ftiper- 

 fluous caloric ; and its particles being no longer kept 

 afunder by a fuperior force, yield to the ordinary im- 

 pulie of attraction, and are condenfed into the (late of 

 a. common fluid. There are, however, permanently 

 elaftic fluids, which are maintained in their claftic (late 

 by the ordinary heat of this earth ; and thefe by ana- 

 logy we may conclude are ccmpofed of particles which 

 have a weak attradtion for each other, and are there- 

 fore preferved in this rare and volatile ftate by a mo- 

 derate portion of the matter of fire interpofed between 

 them : of this kind is the air we breathe, and fome 

 other fluids, of which I fhall prefently have occafion to 

 treat *. 



It would be improper to difmifs this fubject, with. 

 out offering a few remarks on that fpecies of evapora- 

 tion which is termed fpontaneous, as I apprehend it 

 not to be efTentially different from that of which we 

 have been treating. It is evident that a quantity of 

 humidity is continually and infenfibly emitted by every 

 body which contains any principle of moiilure. If a 

 glafs of cold water, or any cold body, fuch as fmooth 

 marble, is expofed in a room when many people are 

 afiembled, its outfide will be covered with dew ; the 

 walls of churches and other buildings which have not 

 conftant fires are covered with moifture in the fame 



* As the ordinary heat of our atmofphere is fufficient to keep 

 water and fome other fubilances fluid ; fo it ferves to keep thefe 

 bodies in a volatile itate. 



manner, 



