244 



auction. One consequence, however, which seems 

 to follow from considering the aqueous vapour to be 

 wholly emitted by the exhalents of the lungs, we 

 cannot omit to notice ; for, on this supposition, there 

 seems no reason to think that any part of the caloric 

 liberated in the lungs by the decomposition of the 

 air, is, as Dr Menzies imagined, employed to raise 

 that fluid/ into vapour. The power of the skin, 

 \vhen its heat is many degrees below that of the 

 lungs, is sufficient to emit its excretion in a vapori- 

 fic form, nor is there any reason why the exhalents 

 of the lungs should not, without the aid of a fresh 

 portion of caloric, emit vapour also. In fact, both 

 the external -and internal surfaces of the body always 

 do so ; and it is only when the exhalation is exces- 

 sive that the insensible perspiration is condensed in- 

 to a fluid form. 



HERE; for the present, the author closes his in- 

 quiry. After the review which has now been taken 

 of the changes induced by living vegetables arid ani- 

 mals on the air, it Was originally his intention to 

 have entered on 'an investigation of the effects 

 which these changes produce upon them. Had he 

 pursued the subject, it was his design, by a strict ap- 

 plication of the preceding facts, to have attempted the 

 illustration of certain phenomena which occur in ger- 

 mination and vegetation ; and likewise in the evolu- 



