MR HAYCRAFT on the Specific Heat of the Gases. 199 



The tubes communicating between the heating vessel and 

 the calorimeters were one inch in length. In these tubes there 

 was an opening, through which could be introduced a delicate 

 thermometer, for the purpose of ascertaining the temperature 

 of the Gases as they entered the calorimeters 



Each of the calorimeters was inclosed in a polished metallic 

 case, for the purpose of preventing, as much as possible, the ab- 

 sorption or escape of caloric during the process. These latter 

 were also placed in a box containing water, which was repeated- 

 ly agitated, that the calorimeters might not be affected by the 

 unequal temperatures of the walls of the apartment. 



For the purpose of facilitating the operation of filling the ap- 

 paratus with the Gas operated upon, there was a turn-cock fixed 

 in the course of each returning tube, by which the current of 

 Gas through the tube was interrupted. Two smaller turn-cocks 

 also were fixed in the same tube, one on each side of the larger 

 turn-cocks : these, when open, communicated with the external 

 atmosphere. When, therefore, the large turn-cock was closed, 

 and the small ones open, the air would necessarily, during the 

 action of the machine, rush in at one of the small turn-cocks, and 

 be forced out of the other, so that the air contained in the ap- 

 paratus would be constantly renewed. In order, then, to fill the 

 machine with the Gas, nothing more was necessary than to form 

 a connection between the gasometer or receiver containing the 

 gas and the apparatus, by means of a tube connected to the small 

 turn-cock first mentioned, through which the air rushed in. In 

 performing this operation, however, I usually made use of an air- 

 pump to exhaust the apparatus, and then opening the turn-cock 

 communicating to the gasometer, filled it with the Gas required : 

 after this operation had been several times repeated, I found 

 the gas contained in the machine to be nearly as pure as that 

 contained in the gasometer. 



