ATMOSPHERIC AIR.

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ATMOSPHERIC AIM.

PART XVIII.

HATEVER has been hitherto stated relative to the dif-ferent kinds of aeriform fluids, is chiefly important, because theknowledge of them is necessary to enable us to comprehend thenature of that gazeous fluid in which we are plunged the mo-ment we are born, and in which we exist. This fluid whichsurrounds the earth to a considerable, but unknown height aboveits surface, is called

THE ATMOSPHERE.

In treating of the different aeriform fluids which have hi-therto been the subject of our consideration, it was necessary insome measure to anticipate the present, and to intimate that theair of our atmosphere is not, as was formerly supposed, a simpleor homogeneous fluid, but that in reality it is composed of twodistinct fluids, called oxigen gas and nitrogen gas.

Strictly speaking, the air of our atmosphere is however not sosimple a substance as to be formed only of two ingredients. Be-sides the two substances of which it is composed, it contains asmall portion of another gazeous fluid, called carbonic acid.

It is also well known that a large portion of water is generallycontained in the atmosphere, besides a great variety of sub-stances which are subject to evaporation, and which are capableof existing in an aeriform state at the usual temperature.

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