SECT. VII. DECOMPOSITION OF WATER. 177 



degree of amelioration is not stated ; and on this 

 account Saussure is of opinion that no conclusion 

 should be founded on the fact, as he had never ob- 

 served any example in which a plant deprived of the 

 contact of carbonic acid had augmented the quantity 

 of oxygene contained in its atmosphere by a quantity 

 exceeding that of its own volume, which he regards 

 as being too little to establish the above conclusion. 



It was next ascertained that plants vegetating in From in- 



.1 . -i . sufficient 



pure water augment their weight, at least in a green data. 

 state, even though confined in an atmosphere of 

 oxygene, or of common air deprived of us carbonic 

 acid. This was thought to be a fact of great im- 

 portance, but it does not yet prove the decomposi- 

 tion of water by the plant, nor the fixation of its 

 oxygene, or hydrogene ; because the augmentation 

 in weight may have been occasioned by the mere 

 introduction of the water into the sap vessels, or cel- 

 lular tissue : and hence the question can be deter- 

 mined only by the evidence of the augmentation of 

 the solid substance of the vegetable in a dried state. 



The first experiments that were instituted with a Experi- 

 view to this object are those of Saussure ; his method 

 was as follows : Having gathered a number of plants 

 of the same species, as nearly alike as possible in all 

 circumstances likely to be affected by the experiment, 

 he dried part of them to the temperature of the at- 

 mosphere, and ascertained their weight ; the rest he 

 made to vegetate in pure water, and in an at- 

 mosphere of pure oxygene, for a given period of time, 



VOL. II. >' 





