in a rock-cleft. It changes to ice with a force almost beyond
measurement in the orderly arrangement of its crystals in compliance
with an immutable law for such arrangement, and rends the rock. The
process goes on. There is no high mountain in any land where water will
not freeze. The water of rain and snow carries away the powdered remains
from year to year, and from age to age. The comminuted ruins of
mountains have made the plains and filled up and choked the mouth of the
Mississippi. The soil that once lay hundreds of miles away has made the
delta of every river that flows into the sea. The endless and resistless
process goes on without ceasing, a force that is never expended, and but
once interrupted within the knowledge of men, then covered a large area
of the world with a sea of ice that buried for ages every living thing.

The common idea of the steam that we make by boiling water is that it is
all water, composed of that and nothing else, and this conception is
gathered from apparent fact. Yet it is not entirely true. Steam is an
invisible vapor in every boiler, and does not become what we know by
sight as steam until it has become partly cooled. As actual steam
uncooled, it is a gas, obeying all the laws of the permanent gases. The
creature of temperature and pressure, it changes from this gaseous form
when their conditions are removed, and in the change becomes visible to
us. Its elasticity, its power of yielding to compression, are enormous,
and it gives back this elasticity of compression with almost
inconceivable readiness and swiftness. To the eye, in watching the
gliding and noiseless movements of one of the great modern engines, the
power of which one has only a vague and inadequate conception seems not
only inexplicable, but gentle. The ponderous iron pieces seem to weigh
nothing. There is a feeling that one might hinder the movement as he
would that of a watch. There is an inability to realize the fact that
one of the mightiest forces of nature is there embodied in an easy,