Chap. 5.] Dr. Crawford's Experiments on 'Boiling. 125 



experiment made with water at a high temperature, 

 A quantity of that fluid having been raifed in Papin's 

 digefter * to a temperature many degrees above the 

 boiling point -J-, was fuffered to communicate with the 

 external air, by opening a ftop-cock, upon which a 

 part of it was inftantly converted into vapour, and the 

 water at the fame moment funk to 212 {.' As it ap- 

 peared however that only a very fmall quantity of the 

 water had been carried off by this fudden evapora- 

 tion, it was naturally concluded that the whole of the 

 fuperfluous fire which the water had previoufly im- 

 bibed was abforbed by that part which afTumed the 

 form of vapour. 



The fact is accounted as eftablifhed by the fame 

 philofopher from the following experiment. If eight 

 pounds of the filings of iron at 212 are mixed with a 

 pound of water at 32, the temperature of the mixture 

 will be nearly I22j the iron will be cooled 90 de- 

 grees, and the water heated 90. But if eight pounds 

 of iron filings at 300 are mixed with a pound of wa- 

 ter at the boiling pointj the temperature of rhe mix- 

 ture will continue at 212, and a part of the water will 

 be fuddenly carried off in vapour, which vapour itfelf 

 will be found to retain the fame temperature of 212. 

 In this experiment the temperature of the iron is low- 

 ered 88 degrees, without any apparent accefllon of 

 heat to the water j the fair conclufion is therefore that 

 the fuperfluous caloric is abforbed and carried off by 

 the vapour ||. 



Vapour is an elaftic fluid, that is, it admits of being 

 compreffed within a compafs proportioned to the force 

 1 ^ 



* Papin's digefter is an iron vefTel, made particularly ftron^. 



*J- I have been told to 412. 



} Crawford on Animal Heat, p. 77. || Ibid. p. 78. 



which 



