100 



on passing lime-water into the jar, the air was 

 diminished ^ part of its bulk ; and v/hen, in a sub- 

 sequent experiment, the residual air was agitated in 

 water, it was reduced between one-fifth and one- 

 sixth of the whole *. Dr Crawford found also, 

 that when the experiment was made over mercury, 

 the diminution was not sensible ; but that, if water 

 of potassa was added to the residual air, it became 

 mild, and the air was diminished in the same de- 

 gree as if the experiment had been made over water, 

 or nearly one-fifth of its bulk f. These variations 

 in the results arise, no doubt, from the more or less 

 complete attraction of the carbonic acid by the fluids 

 over which the experiments were made ; and, from 

 the whole of them, we may collect, that, when mer- 

 cury is employed, which has no attraction for car- 

 bonic acid, the diminution is hardly sensible ; but 

 that when this acid is completely abstracted by an 

 alkaline fluid, the loss of bulk amounts nearly to 

 one-fifth of the whole air employed. This inference 

 corresponds very exactly with the facts which occur 

 in vegetation, and in the respiration of the inferior 

 animals. 



84. But experiments of this nature, although they 

 shew the extent to which the destruction of the oxy- 

 gen gas, contained in a given quantity of air, may, 

 by the process of respiration, be made to proceed, 

 yet they do not apply to the ordinary circumstances 

 in which that function is carried on ; for the air of 



* Observations on Air, vol. v. p. 112. et scq. 

 | On Animal Heat, p. 116. 



