It therefore becomes a point of great interest--what are the
materials of this specimen? What is the constitutional character of
this object, which may be said to be a sample, presented to our
immediate observation, of those crowds of worlds which seem to us as
the particles of the desert sand-cloud in number, and to whose
profusion there are no conceivable local limits?

The solids, liquids, and aeriform fluids of our globe are all, as has
been stated, reducible into fifty-five substances hitherto called
elementary. Six are gases; oxygen, hydrogen, and nitrogen being the
chief. Forty-two are metals, of which eleven are remarkable as
composing, in combination with oxygen, certain earths, as magnesia,
lime, alumin. The remaining six, including carbon, silicon, sulphur,
have not any general appellation.

The gas oxygen is considered as by far the most abundant substance in
our globe. It constitutes a fifth part of our atmosphere, a third
part of water, and a large proportion of every kind of rock in the
crust of the earth. Hydrogen, which forms two-thirds of water, and
enters into some mineral substances, is perhaps next. Nitrogen, of
which the atmosphere is four-fifths composed, must be considered as
an abundant substance. The metal silicium, which unites with oxygen
in nearly equal parts to form silica, the basis of nearly a half of
the rocks in the earth's crust, is, of course, an important
ingredient. Aluminium, the metallic basis of alumin, a large
material in many rocks, is another abundant elementary substance.
So, also, is carbon a small ingredient in the atmosphere, but the
chief constituent of animal and vegetable substances, and of all
fossils which ever were in the latter condition, amongst which coal
takes a conspicuous place. The familiarly-known metals, as iron,