I introduced through water into six phials, one of which contained hydrogene, one oxygene, one common air, one hydrocarbonate, one carbonic acid, and one nitrous oxide, six similar plants of mint, their roots being in contact with water and their leaves exposed to light. The plant in carbonic acid began to fade in less than two days, and in four was dead. That in hydrogene died in less than five days; that in nitrous oxide did not fade much for the first two days, but on the third, drooped very much, and was dead at the same time as that in hydrogene. The plant in oxygene for the first four days, looked flourishing and was certainly of a finer green than before, gradually however, its leaves became spotted with black and dropped off one by one, till at the end of ten days they had all disappeared. At this time the plant in common air looked sickly and yellow, whilst that in hydrocarbonate was greener and more flourishing than ever. I have detailed these experiments not on account of any important conclusions that may be drawn from them; but with a view of inducing others to repeat them, and to examine the changes effected in the gases. If it should be found by future experiments, that hydrocarbonate generally increased vegetation, it would throw some light upon the use of manures, containing putrefying animal and vegetable substances, from which this gas is perpetually evolved. The chemistry of vegetation though immediately connected with agriculture, the art on which we depend for subsistence, has been but little investigated. The discoveries of Priestley and Ingenhousz, seem to prove that it is within the reach of our instruments of experiment. No. II. APPROXIMATIONS TO THE _Composition and Weight of the aëriform_ _COMBINATIONS of NITROGENE_ At temperature 55°, and atmospheric pressure 30.