s called
sulphates. In union with iron it forms sulphide of iron. The "fool's
gold" which Captain John Smith's colonists found in the sand at
Jamestown, was this worthless iron pyrites.

_Chlorine_ is a greenish, yellow gas, very heavy, and dangerous to
inhale. If it gets into the lungs, it settles into the lowest levels,
and one must stand on one's head to get it out. As an element of the
earth's crust it is not very plentiful, but it is a part of all the
chlorides of sodium, magnesium, and potassium. In salt, it forms two per
cent. of the sea water. It is much less abundant in the rocks.

To these elements we might add _nitrogen_, that invisible gas which
forms nearly four-fifths of our atmosphere, and is a most important
element of plant food in the soil. Most of the seventy elements are very
rare. Many are metals, like gold and iron and silver. Some are not
metals. Some are solid. A few are liquid, like the metal mercury, and
several are gaseous. Some are free and pure, and show no disposition to
unite with others. Nuggets of gold are examples of this. Some exist only
in union with other elements. This is the common rule among the
elements. Changes are constantly going on. The elements are constantly
abandoning old partnerships and forming new ones. Growth and decay of
plant and animal life are but parts of the great programme of constant
change which is going on and has been in progress since the world
began.

THE FIRST DRY LAND

When the earth's crust first formed it was still hot, though not so hot
as when it was a mass of melted, glowing substance. As it moved through
the cold spaces of the sky, it lost more heat and its crust became
thicker. At length the cloud masses became condensed enough to fall in
torrents of water, and a great sea covered all the land. This was before
any living thing, plant or animal, existed on our planet. Can you
imagine the continents and islands that form the land part of a map or
globe suddenly overwhelmed by the oceans, the names and boundaries of
which you have taken such pains to learn in the study of geography? The
globe would be one blank of blue water, and geography would be
abolished--and there would be nobody to study it. Possibly the fishes in
the sea might not notice any change in the course of their lives, except
when they swam among the ruins of buried cities and peered into the
windows of high buildings, or wondered what new kind of seaweed it was
when they