Chap, 4.] faffing from a fluid to ajcltd State, 13 c. 121 

 of heat) are abforbed, or reduced to a ftate of combi- 

 nation, fo as not to produce any effect on the thermo- 

 meter *. 



The heat which the water abforbs in afTuming its 

 fluid form is again feparated by congelation, if a 

 pound of water at 32 is mixed with an equal quan- 

 tity of ice at 4, nearly one fifth of the water will be 

 frozen, and the temperature of the mixture will be 32. 

 In this experiment the ice is raifed from 4 to the 

 freezing point. It is therefore evident;, in this expe- 

 riment, that by the congelation of one-fifth of the wa- 

 ter a quantity of caloric is emitted fufficient to raife the 

 heat of the ice nearly twenty-eight degrees; by the con- 

 gelation therefore of ar whole pound of water 3 a quan- 

 tity of caloric would be detached fufficient to raife it 

 five times twenty-eight degrees. The caloric which 

 is extricated by the congelation of the water is there- 

 fore precifely equal to that which is abforbed by the 

 melting of ice f. 



There were difputes in the time of Fahrenheit, con- 

 cerning the rarefaction of ice, whether it depended on 

 the air contained in it during its fluidity. He ima- 

 gined, that if he extracted the air from water, he could 

 produce an ice heavier than water. He extracted the 

 air therefore from fmall glafs globes filled with water. 

 After expofing them to an intenfe cold, they were a 

 long time in freezing, though cooled greatly below 

 the freezing point ; but upon breaking them to exa- 

 mine them, the air ruihed in, which, from the fudden 

 fhock, occafioned the water inftantly to freeze. He 

 afterwards found, that fimple agitation would produce 

 the fame effect. If water which is freed from air, and 

 which is perfexftly at reft, is expofed to the atmo- 

 fpherewhen it is colder than 32, it will frequently fink 



* Crawford on Animal Heat, p. 72. f Ibid. 



eiirht 



