68 
and carbonic acid, and exposed to the solar influ- 
ence, this acid gas will be changed into an air insolu- 
ble in water*. Lastly, we may add, that the rapid 
manner in which the purification of the air is stated 
to have occurred in the experiments of Dr Ingen- 
housz, effectually excludes the idea of the oxygen 
gas being derived from decomposition of the vegeta- 
ble substance. 
298. M. Senebier instituted, likewise, a grea' num- 
ber of experiments to prove the production of oxy- 
gen gas by plants, exposed to the direct rays of the 
sun. Almost all of them were, however, made by 
immersing leaves in water, previously impregnated 
Avith carbonic acid ; and they do not apply, there- 
fore, directly to the present question. In one instance, 
indeed, he placed a branch of raspberry tree, having 
its end dipped in water, in a recipient rilled with 
common air, and inverted in water. The recipient 
was then exposed, through the day, to the direct in- 
fluence of the sun. The air at first, when examined 
by nitrous gas, was reduced to 1 .04, and at the close 
of the experiment, when again tried, it was reduced 
to 1 .00 ; so that, if the method of analysis be deemed 
correct, it had experienced some improvement. 
299 M. Senebier considers the agency of the sun 
to be indispensable to the production of the oxygen 
gas which leaves afford, when confined either in wa- 
ter or in air ; and this operation of light, he adds, is 
continued through the winter, by those plants which 
retain their verdure. He has seen mosses, when pla- 
* Kxper. t. ii. p. /4. 7\ 
