270 Prof. Apjohn o« the Specific Heats of the GaseSf 



been generally adopted, appeared to me much too great to 

 admit of being referred to error of experiment. I was there- 

 fore very anxious to return to the subject, and towards the 

 end of July 1836, I undertook a fresh series of experiments, 

 which were conducted on the following plan. 



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A pair of copper gasometers, A, B, with glass bells, C, D, 

 such as are usually employed by chemical lecturers, were 

 charged with a proper quantity of oil of vitriol, instead of 

 water, and placed upon a table at the distance of three feet 

 from each other, the brass caps, E, F, attached to the bells, 

 being suspended to the extremities of a stout cord passing 

 over a pair of pulleys, G, H, fixed in the ceiling of the la- 

 boratory, the length of the cord being such that while one of 

 the bells was almost entirely immersed in the oilof vitriol, the 

 other dipped about an inch beneath its surface. Between the 

 lower stopcocks, m, n, attached to the gasometers, a couple 

 of glass tubes were interposed, connected to the stopcocks by 

 caoutchouc collars, and fitting at their other extremities to 

 each other by a tight ground joint. In the larger of these 

 tubes the dry thermometer i was permanently placed, and into 

 it the wet one t' was also introduced previous to the com- 

 mencement of an experiment. Matters being, we shall sup- 

 pose thus prepared, and the unimmersed bell, C, occupied, 



