CLASSIFICATION OF GASES.

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atmospheric air, analogous to that occasioned by their submer-sion in water.

Others again produce some positive change in the blood, asappears from the experiments of Dr. Beddoes and Professor Davy.They seem to render it incapable of supplying the nervous andmuscular fibres with principles essential to sensibility and irrita-bility. These gases therefore destroy animal life on a differentprinciple.

It is obvious therefore that the above classification does nothold good in all respects, but is capable of misleading the stu-dent. We shall not divide the gases we are going to treat ofinto different classes ; for we do not see the advantage which canarise from any division: we shall therefore examine first thosewhich are simple, the bases of which cannot be exhibited inan insulated state, namely, oxigen, nitrogen, and hidrogen gas.We shall then consider the combination of these gases with eachother, in order to understand some of the most important phe-nomena in which they are concerned, together with the rest ofof those gases, of which the bases may be exhibited experi-mentally.

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