49 
diminished the oxygen gas of the air, and formed 
carbonic acid *. Many facts of a similar kind are to 
be met with in different parts of his work f 
268. With the view of confirming these facts, we 
placed some young mustard plants in a jar containing 
40 cubic inches of atmospheric air. They were sup- 
ported on a small whalebone hoop, covered with 
netting, beneath which a small cup, containing wa- 
ter of potassa, was placed. The jar stood inverted 
in a saucer of mercury ; and at eight o'clock in the 
evening, when the temperature was 60 Fahrenheit, 
it was set aside in a dark room. By seven o'clock 
the next morning, the mercury had risen three- 
tenths of an inch into the jar ; and, on raising the 
jar and pouring diluted acid into the alkaline solu- 
tion, a brisk effervescence was excited, proving, in 
the usual manner, the conversion of the oxygen gas 
of the air into carbonic acid. In many subsequent 
observations on the vegetation of young beans in 
jars of atmospheric air, we likewise remarked their 
growth in the night, when the temperature was suf- 
ficiently high, to be little inferior to that which they 
make in the day ; a fact which is exemplified equally 
in the warmer regions of the globe, where a rapid suc- 
cession of crops is obtained, and in high northern lati- 
tudes, where the short season of summer permits the 
intervention only of a few weeks between the pe- 
riods of seed-time and of harvest. 
* Exper. &c. t. ii. p. 117 118, 
t Ibid. vol. ii. p, 45. 46. 
B 
