MR HAYCRAFT on the Specific Heat of the Gases. 201 



lowance for the imperfection of all instruments. Each calorime- 

 ter was furnished with its thermometer, the bulb of which was 

 placed equidistant from its four sides : two smaller ones were 

 placed so as to ascertain the temperature of the Gases before 

 entering into, or coming out, of the calorimeter. One was at- 

 tached to the heating vessel, and another to the vessel of water 

 which served as the surrounding medium of the calorimeters. 



Having filled both the calorimeters with water of the tem- 

 perature of 42, and the heating vessel with it at a temperature 

 of about 1 80, I admitted atmospheric air into each part of the 

 apparatus. The pistons were put into motion, and continued till 

 each of the calorimeters arrived at a temperature of 84, with a 

 variation of little more than one-twentieth part of a degree. 

 Thus the temperature of the calorimeters was raised 42 each, 

 with a correction of T 7 th part of the whole. Much greater al- 

 lowances may very properly be made for the imperfections of the 

 instruments. This experiment was designed to prove the accu- 

 racy of the apparatus, and was often repeated, at different periods* 

 with the same event. I was assisted in the following experi- 

 ments by my friend Dr CLENDINNING, to whom I am much in- 

 debted for their success. 



Experiments on Carbonic Acid. 

 No. 1. 



The part of the apparatus which I call A was filled with car- 

 bonic acid, obtained from carbonate of lime ; the part B with 

 common air. In each of the cylinders was placed, in a proper 

 receptacle, a quantity of very dry muriate of lime, for the pur- 

 pose of perfectly freeing the Gases from watery vapour. The ca- 

 lorimeters being filled with water at a temperature of 42, and 

 the heating vessels with water at 149^|, the following results 

 were obtained. 



VOL. x. P ij e e 



