Page:The fairy tales of science.djvu/57

Rh all living beings would be suffocated and die." In all ages the atmosphere has been regarded as the great source of life, and long before the famous dogma of the Four Elements was propounded, a Grecian sage declared that air was the one universal principle from which everything proceeded.

We have already alluded to the fact that combustible bodies combine with a certain gas called oxygen, which is contained in the atmosphere; our readers will not, therefore, be surprised when we tell them that air is a mixture of dissimilar gases, but they will marvel greatly when we describe the properties of its constituents.

If we boil some mercury or quicksilver in a closed glass vessel, in a few hours the metal will undergo a very extraordinary change. It will lose its metallic character entirely, and in place of the glistening fluid we shall find a heap of bright red scales. As these scales weigh more than the original mercury, we may safely conclude that something has been abstracted from the air contained in the vessel.

If we now take a lighted match and plunge it into the air that remains, it will be instantly extinguished; it is therefore evident that the abstracted something is oxygen.

Let us close the vessel once more and apply to it a strong heat; the red scales are now converted into metallic mercury, and the air regains its property of supporting combustion.