so 
as by the germination of seeds, and that no part of 
the oxygenous portion of the atmosphere combines 
with the substance of the plant. 
240. It may, perhaps, add weight to the forego- 
ing conclusions, if we are able to shew, that, not- 
withstanding the apparent contrariety of fact and o- 
pinion which has prevailed on this subject, the wri- 
tings of various authors furnish decisive evidence that 
growing vegetables produce in the air those specific 
changes, which we have held to be essential to vege- 
tation. Even so far back as the time of Dr Hales, 
an experiment is related which entirely accords with 
these views. That eminent philosopher set a plant 
of peppermint, on the 29th of June, in a glass cistern 
of earth, and filled it with water. Over this cistern 
he inverted a glass vessel, and then drew out part of 
the air by a syphon, so as to leave 49 cubic inches 
of air in the vessel. By the side of this vessel he 
placed another of the same size, inverted in a si- 
milar manner, but without any plant beneath it. 
In a month, the mint in the first vessel had put forth 
several young shoots. The water, in both vessels, 
rose and fell with the variations in atmospheric pres- 
sure and temperature ; but the water, in which the 
peppermint stood, rose so much above its first fixed 
station, and above that in the other vessel, that one- 
seventh part of the air must, says Dr Hales, have been 
reduced to a fixed state. This happened chiefly in 
the summer months. In the beginning of the fol- 
lowing April, the old mint was taken out ? and a 
