nt carbon is found in abundance and in strangely different
combinations. As a gas, in combination with oxygen, it is breathed out
of our lungs, and out of chimneys where coal and wood are burned. It
forms a large part of the framework of trees and other plants, and
remains as charcoal when the wood is slowly burned under a close
covering. There is a good proportion of carbon in animal bodies, in the
bones as well as the soft parts, and carbon is plentiful in the mineral
substances of the earth.

The chemist is the man who has determined for us the existence and the
distribution of the seventy elements. He finds them in the solid
substances of the globe and in the water that covers four-fifths of its
surface; in the atmosphere that covers sea and land, and in all the
living forms of plants and animals that live in the seas and on the
land. By means of an instrument called the spectroscope, the heavenly
bodies are proved to be made of the same substances that are found in
the rocks. The sun tells what it is made of, and one proof that the
earth is a child of the sun is in the fact that the same elements are
found in the substance of both.

Of the seventy elements, the most important are these: Oxygen, silicon,
aluminum, iron, manganese, calcium, magnesium, potassium, sodium,
carbon, hydrogen, phosphorus, sulphur, chlorine, nitrogen.

_Oxygen_ is the most plentiful and the most important element. One-fifth
of the air we breathe is oxygen; one-third of the water we drink. The
rock foundations of the earth are nearly one-half oxygen. No fire can
burn, no plant or animal can grow, or even decay after it dies, unless
oxygen is present and takes an active part in each process. Strangely
enough, this wonderful element is invisible. We open a window, and pure
air, rich in oxygen, comes in and takes the place of the bad air but we
cannot see the change. Water we see, but if the oxygen and the hydrogen
which compose the colourless liquid were separated, each would become at
once an invisible gas. The oxygen of solid rocks exists only in
combination with other elements.

_Silicon_ is the element which, united with oxygen, makes the rock
called quartz. On the seashore the children are busy with their pails
and shovels digging in the white, clean sand. These grains are of
quartz,--fine crystals of a rock which forms nearly three-quarters of
the solid earth's substance. Not only in rocks, but out here in the
garden, the soil is ful