44 
they were confined, was diminished one cubic inch 
and a half : its purity, also, was greatly impaired ; 
and it contained -rf^ of carbonic acid. Experiments 
made with plants of mint, in the shade, afforded si- 
milar results -, but when the apparatus was exposed, 
for the same time, to the direct agency of the solar 
rays, the air experienced no change, either in its 
purity or its volume. From these and other experi- 
ments, M. de Saussure concludes, that plants, like 
animals, continually form carbonic acid, when they 
vegetate in atmospheric air, either in the sunshine or 
in the shade ; that the oxygen of the air contributes 
to the formation of this acid ; and that the reason 
why carbonic acid is not detected in the apparatus 
exposed to the sun, is, because it is then decomposed 
as fast as it is formed *, 
261. In subsequent experiments, relating to vege- 
tation t? M. de Saussure directed his attention almost 
entirely to ascertain the influence of solar light in de- 
composing carbonic acid. With this view he con- 
fined plants in mixed atmospheres of common air 
and carbonic acid gas, and exposed the apparatus to 
the direct rays of the sun, whereby he obtained very 
different results. We shall, therefore, postpone our 
report of these experiments to a future occasion, ob- 
serving, for the present, that the experiments related 
above, accord entirely, in their results, with our own, 
and with those of other writers, respecting the effects 
produced in atmospheric air, by plants which vege* 
tate in the shade. 
* Annales de Chimie, t. xxiv. p. 139. et seq. 
t Recherches Chim. sur la Vegetat, 
