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TuE proportion in which inflammable gas contributes to vege- 

 table greennefs feems to be afcertained by forae late obfervations. 

 M. Ingenhoufz has remarked, that when this gas is mingled with 

 the air in which vegetables grow, the verdure of the latter acquires 

 a much deeper fliade. M. Humboldt found that divers plants of 

 the clafs cryptogamia pufh out green ftalks, though placed in mi- 

 neral pits where light has no accefs ioi them ; and that feveral of 

 the gramina have green leaves when growing in the galleries of 

 certain mines, at the depth of 360 feet beneath the furface of the 

 earth. On examining the air in thefe fituations, he found that it 

 was mingled with hydrogenous gas. Thefe curious phenomena, 

 which M. Humboldt employs in a fatisfadtory manner to explain 

 the etiolation (blanching) of plants, tend equally to render it pro- 

 bable that this gas has at leaft fome fhare in giving the foft-toned 

 green, the delightful colour of nature^ to the vegetable creation. 

 As rain-water, however, is found to contain, in a ftate of folution 

 (not in combination like fnow) a portion of oxygene, and as the 

 contad of oxygene expedites the germination of feeds, a fhare in 

 producing the verdure of our winters may of courfe devolve on 

 atmofpherical moifture and warmth. But I queftion whether to 

 thefe caufes can be legitimately afcribed the whole of the verdure, 

 as after the diiTolution of deep fnow, (which is more oxygenated 

 than rain-water, and which, being a bad condudlor of caloric, 

 confines the atmofpherical heat,) the greennefs of plants is much 



paler, 



