that have occurred from time to time, and to the successive
"ages" of the layers of rock foundation of its crust, there are many
mysteries that remain unsolved and many questions will present
themselves to the mind of the reader. One of these questions is, Where
was the water and where was the earthy matter before its precipitation?
Matter, including water, can exist in the gaseous form, and we only need
to assume that there was a core of intense heat, to understand how all
the material that we find on the earth and in the earth could have been
held in suspension in the gaseous state until the cooling process had
reached a stage where the various combinations and recombinations could
take place in the great laboratory of nature. If we study the
constitution of the sun (and with the modern appliances we are able to
do so), we find that it is made up of some and perhaps all of the same
materials that are found here on earth. If there is no water existing,
in the sun, as water, there are the gases present which would produce it
if the conditions were right. And, for all we know, that flaming mass of
burning gases may some time go through the same kind of cooling and
building up in solids that our earth has experienced.

We thus have what may be called an outline sketch of the process of
World-building.

CHAPTER II.

LIMESTONE.

A large part of the structure of the earth's crust is formed of a
substance called limestone. Ordinary limestone is a compound of common
lime and carbon dioxide, a gas that is found mixed with the air to a
very small degree. Carbon dioxide will be better known by the older
people as carbonic acid. It is a gas that is given off whenever wood and
coal are burned, or any substance containing carbon. It is composed of
one atom of carbon to two of oxygen. Every ton of coal that is burned
sends off three and two-thirds tons of this gas. The increase in weight
comes from the fact that every atom of carbon unites with two of oxygen,
which it takes from the air, and the oxygen is heavier than the carbon.

In comparing the relative weights of atoms (the smallest combinable
particle of a solid, liquid, or gas) we use the hydrogen atom as the
unit of comparison and call it "one," because it is the lightest of all
atoms. The carbon atom is twelve times heavier than the hydrogen atom,
and the oxygen atom is sixteen times heavier. Hence it will be seen
readily how a ton of coal will form two and two-