r'efpcSltng Heat or Caloric. 217 



fot the convenience of feeing. The exterior vefiel has an 

 Opening at the top C, into which is fitted a glafs tube CD. 

 Through this tube (or before fixing the tube in its pbce) fill 

 the fpace between the interior and exterior vefiel with any 

 coloured liquid. 



If this double vefiel be now filled with, and immerfed in, 

 warm water, it is plain that the heat thus communicated to 

 it will expand the coloured liquid contained between the in- 

 terior and exterior fui faces, and make it rife to fuch a height 

 in the glafs tube as fiiall correfpond to the temperature of the 

 water in which it is immerfed. By employing water of dif- 

 ferent temperatures the different degrees of heat, as afcer- 

 tained by an accurate thermometer, may be marked upon the 

 tube, or on a fcale attached to it ; arid thus the vefiel itfelf 

 will, in fact, become a large hollow thermometer. 



To the lower end of the cock B attach another vefiel E, 

 made of caft iron, furnifhed with two other cocks, a and b, 

 rind connected with the vertical tube FG, made of iron (a 

 feries of giin barrels properly joined to each other) or of glafs, 

 fecured by a cafe of wood, with cement interpofed between 

 it and the glafs. 



Provide alfo a vefiel of the fame capacity as the internal 

 dimerifions of the gas-holder A. This vefiel may be called 

 the meafure. 



From the above fhort defcription the cOnftruction of the 

 gafo-calorimeter, its ufe, and the way of operating with it, 

 may be eafily conceived. 



Open the cocks a and F, and pour mercury into the 

 funnel at G. It will rife ih E, driving the air before it, 

 which will efcape by the cock a. Having in this way filled^ 

 the vefiel E with mercury up to the cock B, fliut the cock F, 

 place the meafure before mentioned below the cock b, and 

 by that cock draw OfT one meafure of the mercury. It is 

 obvious that by fo doing one meafure of air will at the fame 

 time pafs into E through the cock a *. The cocks a b being 

 now fhut, pour mercury into the tube FG to any convenient 

 height; open the cock B, and then the cock F. The mea- 



• Any other gas may be introduced by connecting this cock, with a 

 pneumatic apparatus. 



Voi. VIII. Ff fare 



