Mr. Haycraft on the Specific Heat of the Gases. 205 



lorimeter every minute. There was no occasion, however, to 

 take these quantities into the account, because they were pre- 

 cisely the same of each gas subjected to trial. 



My thermometers were adjusted by Mr. Adie of Edinburgh. 

 Each degree was divided into 5 parts, which were sufficiently 

 large to be divided by the eye into 4 parts; so that the tem- 

 perature could be ascertained to a 20th part of a degree, 

 making allowance for the imperfection of all instruments. 

 Each calorimeter 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 attached 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 4-2°, and the heating vessel with it at a temperature 

 of about 180°, I admitted atmospheric air into each part of 

 the apparatus. The pistons were put into motion, and con- 

 tinued 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 F ^th part of the whole. 

 Much greater allowances may very properly be made for the 

 imperfections of the instruments. This experiment was de- 

 signed to prove the accuracy of the apparatus, and was often 

 repeated, at different periods, with the same event. I was 

 assisted in the following experiments by my friend Dr. Clen- 

 dinning, to whom I am much indebted for their success. 



Experiments on Carbonic Acid. 



No. 1. 



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

 carbonic 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 purpose of perfectly freeing the gases from watery vapour. 

 The calorimeters being filled with water at a temperature of 

 42°, and the heating vessels with water at 149°£§ , the following 

 results were obtained. 



Tern- 



