340 
since, as has been well observed, this acid could not 
furnish to plants more of its base than it had previ- 
ously taken from them *. When, too, we consider 
the almost inappreciable quantity of carbonic acid 
that exists in the atmosphere, and call to mind that 
its proportion remains uniformly the same, whether 
vegetation continue or be suspended, we cannot bring 
ourselves to believe, setting aside all physiological 
objections to this mode of nutrition, that plants ob- 
tain from the atmosphere any portion whatever of 
that carbon which administers to their nutrition and 
growth. 
645 From the following experiment of M. Era- 
connot we learn, likewise, that plants, during their 
vegetation, may considerably augment their propor- 
tion of carbonic matter in situations in which no car- 
bon can be supposed to be derived from the atmo- 
sphere that surrounds them. He confined 460 
seeds of white mustard in a large glass bottle, 
filled in part with very fine white sand, which 
was previously deprived of all calcareous earth 
by washing it in muriatic acid. This sand he 
then moistened with distilled water, and filled the 
remainder of the bottle with atmospheric air, freed 
from carbonic acid. After closing the bottles 
very accurately, they were placed a few inches 
deep in a moist soil, Vegetation soon commenced, 
and considerable verdure was produced. At the end 
of six weeks, the plants were taken out of the bottle, 
and washed with great care, and dried. In this state, 
Nicholson's Journal, vol. xviii. p. 22. 
