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



of 61°/q5 the surrounding medium being 54;°- 16, indicating 

 the air of respiration to be 6875. 

 No. 2. 

 The last experiment was repeated, when the calorimeter 



arose from 56°/o to 58 °i%> and B from 56 Vo to 5 7°su> in " 

 dicating the capacity of the air of respiration to be, as in the 

 last experiment, 6875. 



It may not be improper in this place to state, that in my for- 

 mer experiments mixtures of carbonic acid and atmospheric air, 

 under different conditions of temperature, and combination with 

 watery vapour, had relative capacities of 3333,66666*9999, 

 and 13333. It was my intention to have repeated those ex- 

 periments in such a way as to ascertain the precise conditions 

 under which these changes of capacities took place ; but, from 

 various engagements, I am unable to do so. I may remark, 

 however, that the last two experiments seem to indicate, that 

 the air of respiration enters into the second of this series, 

 making allowance for the difference of the standard of com- 

 parison ; this being in my former experiments common un- 

 dried atmospherical air, while the standard of the latter was 

 the same air carefully dried. 



There is also a curious coincidence between this last-men- 

 tioned series of capacities of gas in different states of combina- 

 tion with water, and the expansive forces of air combined also 

 with different proportions of watery vapours. Having pro- 

 cured a glass globe, to which a small stem was connected, in 

 such a way that mercury contained in the hollow ball would 

 rise into the stem upon any increase of the expansive force of 

 the air contained in the ball, I filled the latter with air at a 

 temperature of 60° ; after which the ball was immersed into 

 boiling water. In a short time the mercury rose into the stem 

 to the height of 7 inches. The experiment was repeated, ex- 

 cepting that a few drops of water were put, together with the 

 air, into the ball. The mercury, after the immersion of the 

 ball in boiling water, rose to 21 inches. Afterwards, on pass- 

 ing a quantity of water into the ball, the mercury, after its 

 immersion, rose to 28 inches. Some months afterwards, on 

 repeating the experiment, the mercury rose in one instance to 

 14 inches. Thus we have a series of expansive forces of air 

 united to watery vapour of 7, 14, 21 and 28 inches: it was 

 upon this principle that I contrived an air thermometer. The 

 form of it is similar to that of the differential thermometer in- 

 vented by Professor Leslie. One ball contained atmospheri- 

 cal air dried by means of muriate of lime ; the other contained 

 air in its usual state. Interposed between the balls was a co- 

 lumn 



