2i8 Examination of the received Do&rineS 



fure of air contained in the veffel E, having now no way M 

 efcape, will, by the afcent of the mercury in E> be forced to 

 pafs through the cock B into the gas-holder A. As foon ad 

 this is perceived, by the mercury fhowing itl'elf in the glals 

 cock B, (hut that cock. 



The gas-holder will thus become charged with two atmo-» 

 fpheres, and that in a way fo expeditious as to allow but 

 little time for the efcapc and lofs of caloric, efpccially if the 

 tube FG be of large diameter, and if the veffel E have been 

 previouflv lined, and the veffel A covered over with fume 

 bad conductor of heat. The exprefl'ed heat mnft then pals 

 through the fides of the gafo-calorimeter, and there, exer- 

 cifing its aclion on the interpofed thennometric fluid, mud- 

 make it afcend in the tube CD to a height proportioned to 

 the heat thus communicated to the fluid *. 



Another atmofphere may be introduced by (hutting the 

 cock F, opening a and b, and withdrawing another meafurc 

 of mercury as before, and then, by mercury poured into GF, 

 making the air to afcend into A, in the manner already dc- 

 feribedt. Then note again the height to which the thcr- 

 mometric fluid rifes in CD; and fo of a fourth or a fifth 

 atmofphere ; obferving that the height of the column of mer- 

 cury in FG muft always be proportioned to the number, of 

 atmofpheres to be introduced. 



The quantity of coloured fluid contained between the ex- 

 terior and interior of the double veffel A, fhould be deter- 

 mined by weighing the quantity introduced before gradu- 

 ating the tube CD. By this means it will be poflible to de- 

 termine not merely how many degrees the heat expreffed from 

 the air raifes the fluid in the tube CD, but to how many 

 ounces of the fluid it communicates that degree of tempera- 

 ture. The weight of the materials of which the double veffel 



* As mercury is found to be a good conductor of heat, it would be 

 advifable to have a little oil, or fomc other liquid, in the veffel E, before 

 the fvft introduction of the mercury. The oil would rife on its furface, 

 and the interpofed ftratum riling with the mercury prevent its contact with 

 the air driven before it into the veffel A. 



f Or two or rfiore atmpfphcies may be forced up at oiice, if the veffel E 

 he made of lufficient capacity. 



