122 Phenomena of freezing. [Book II. 



eight: or ten degrees below the freezing point, with- 

 out undergoing any degree of congelation ; but if the 

 veiTel is flightly agitated, a portion of it will imme- 

 diately become folid, and the mixture of ice and wa- 

 ter will be raifed to 32. The reafon of this increafe 

 of temperature in the remaining water will be evident 

 from the preceding experiments. By the freezing of 

 a part of the water, a quantity of elementary fire, 

 which exifled in the fluid, is expelled, by its afFuming 

 a folid form ; and this fire being difTufed among the 

 remaining water, raifes its temperature to the freez- 

 ing point. 



Different degrees of heat are required to retain 

 different bodies in a fluid form. Water, mercury, 

 and fome other fubftance?, are kept fluid by a degree 

 of heat considerably below the ordinary heat of the 

 atmofphere ; and fo great is the degree of cold which 

 the latter endures, that before the experiments of Pro- 

 feflbr Braun, of Peterfburgh, it was not fuppofed that 

 it was capable of being frozen. 



