on Experiments on Vegetation, . 357 
days and nights; and his experiments are the more unexception- 
able, as the plants in many of them grewin their natural states, 
and the shoots or branches from tiem only were introduced 
‘through water into the confined atmosphere.”’ And the next is 
‘Sir Humphry’s own experiment, p. 197: “* The following experi- 
ment I consider as conducted under circumstances more analo- 
gous to those existing in nature. A turf four inches square from 
an irrigated meadow clothed with common meadow grass, mea- 
dow fox-tail grass, and vernal meadow grass, was placed in a 
porcelain dish, which swam on the surface of water impregnated 
with carbonic acid gas: avessel of thin flint glass, of the capacity 
of 230 cubical inches, having a funnel furnished with a stop-cock 
inserted in the top, was made to cover the grass, and the appa- 
ratus was exposed in an open place. A small quantity of water 
was daily supplied to the grass by the means of the stop-cock. 
Every day likewise a certain quantity of water was removed by 
a siphon, and water saturated with carbonic acid gas was sup- 
plied in its place, so that it may be presumed that a small quan- 
tity of carbonic acid gas was constantly present in the receiver. 
*¢ On the 7th of July 1807, the first day of the experiment, the 
weather was cloudy in the morning, but fine in the afternoon, 
the thermometer at 67°, the barometer 30.2. At ten on the 
morning of the 15th, I examined a portion of the gas; it con- 
tained less than 1-50th of carbonic acid gas, 100 parts of it ex- 
posed to the impregnated solution left only 75 parts;” (100 parts 
of the air of the garden occasioned a diminution to 79) ‘so 
that the air was four per cent. purer than the air of the atmo- 
sphere; another similar experiment was made with equally de- 
cisive result.’ p. 199. ‘* These facts confirm the popular opi- 
nion”’ (the old story) © that when the leaves of vegetables per- 
form their healthy functions, they tend to purify the atmosphere, 
in the common variations of weather, and changes from light 
to darkness.’” Are not these principles or opinions the very 
same as those promulgated by Dr. Priestley? Aye, and by Dr. 
Ingenhousz too? Yet W. H. G. represents Sir H. as one of the 
experimental opposers of that very system he is actually advo- 
‘cating. From these repeated misrepresentations on doctrinal 
points on the part of W.H.G., it is even difficult to believe that 
he himself knew which side of the question the above authors 
maintain. We here sce that Sir H. did not consider himself as 
betraying unpardonable ignorance vy publishing his ‘¢ Views and 
Experiments,” although they had been detailed by Drs. Priestley 
and Ingenhousz, many years before, and of course had * antici- 
pated” his views, 
Again. He says, “'The question sti// remaining is, not whether 
plants have the power of counteracting the vitiation pee 
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