SECT. VI. ELABORATION OF OXYGENE. 



but still attached to the stem, which he luted to the 

 neck of the tube. The tube was then placed over 

 mercury. Two hours after sun-set the mercury rose 

 one and a half line within the tube, corresponding 

 to about half the volume of the Branch. On the 

 following morning the mercury was found to have de- 

 scended a little ; and about two hours after the rising 

 of the sun it was as at the commencement of the ex- 

 periment. The air contained A_ of carbonic acid, 

 and -Jy T of oxygene. The branch had then consumed 

 in the space of 24 hours more than five times its vo- 

 lume of oxygene, which it had replaced by scarcely 

 three times its volume of carbonic acid. Now 

 the disproportion between the quantity of oxygene 

 and carbonic acid remaining, was evidently owing to 

 the circumstances of the latter's being carried off to 

 the leaves by means of the branch. But there was 

 formed also in the tube a very considerable quantity 

 of nitrogene, for the volume of its contained at- 

 mosphere was not changed, which Saussure accounts 

 for as follows : As the branch inhales the oxygene 

 of its atmosphere a vacuum is formed in the tube, in 

 consequence of which the external atmospheric air 

 penetrates the porous substance of the branch, and 

 insinuates itself into the atmosphere within; the 

 oxygene of this new atmosphere is absorbed by the 

 branch, and its nitrogene left behind : and hence 

 the proportion of nitrogene in the atmosphere of the 

 tube is of necessity augmented. 



If this experiment is made with water instead of 



1 



