28 
237. We still farther varied these experiments, by 
taking up a young bean out of the pot in which it 
was growing, and carefully washing all the mould 
from its roots. The plant was about seven inches 
high, and its roots were put into a cubic inch glass 
measure, nearly filled with water, on the 20th Au- 
gust, when the thermometer was at 66. The glass 
measure was then put into an egg-cup containing one 
cubic inch of the water of potassa, and the egg-cup 
was placed in a deep saucer. A bell-shaped jar, of 
the capacity of 86 cubic inches, containing atmosphe- 
ric air, was then inverted over the plant, and mer- 
cury poured round its mouth, to cut off the com- 
munication with the external air ; a small stra- 
tum of water, about -Ar of an inch deep, being 
poured on the surface of the mercury. By the 
21st, the plant had grown more than one-fourth 
of an inch above a thread which had been tied 
round the jar to mark its height, and the mer- 
cury had risen a little into the jar. By the 22d, the 
mercury was about -r& of an inch high in the jar, and 
the plant was still growing. By the 23d, the mer- 
cury stood A of an inch high in the jar, and not- 
withstanding the film of water that covered the mer- 
cury, the lower leaves were much discoloured. We 
therefore put an end to the experiment, by raising 
the jar out of the mercury ; and then passing the al- 
kaline solution into a small jar of mercury immersed 
in a bason of that fluid, we obtained, by adding to it 
a due quantity of diluted sulphuric acid, about one 
cubic inch of carbonic acid gas. Now, the diminution 
in the volume of air, in this experiment, must have 
