SECT. VII. DECOMPOSITION OF WATER. 179 



augmented their solid vegetable substance by some- 

 what more than two grains, which could have been 

 acquired only by the assimilation of the oxygene and 

 hydrogene of the water, which they had consequently 

 decomposed. But when the experiment was pro- 

 longed to double or treble the time, the weight of 

 the dried vegetable substance of the plants was not 

 farther augmented ; for which reason, added to that 

 of the small amount of their augmentation, Saussure 

 did not regard the proof from these experiments as 

 being altogether complete, and began to suspect that 

 the oxygene and hydrogene of the plant cannot, 

 perhaps, be assimilated by the plant in any consi- 

 derable degree, unless the augmentation of its carbon 

 is effected in the same proportion. 



The next thing to be done, therefore, was to place 

 his plants in a mixture of common air and carbonic 

 acid gas, that they might have the privilege of assi- 

 milating carbon at the same time ; the results were 

 now more perceptible and more decided, the solid 

 vegetable substance of the plant was evidently in- 

 creased in a greater proportion than could have 

 arisen from the mere presence of carbonic acid. 

 Seven plants of the Vinca minor, vegetating in pure 

 water in a receiver filled with common air and car- 

 bonic acid gas, assimilated in the space of six days 

 the carbon contained in 21-|- cubic inches, or a 

 quantity equal to 4'2 grains ; they assimilated at the 

 same time seven cubic inches of oxygene, but as 



N 2 



