river
is on a much higher level. So we must not think that the springs contain
only the water that feeds the rivers. They contain more.

The layers of clay at different levels, from the surface down to the
bottom of the drift, form water basins and make it possible for people
to obtain a water supply without the expense of digging deep wells. The
clayey subsoil, only a few feet below the surface, checks the downward
course of the water, so that the sun can gradually draw it back, and
keep a supply where plant roots can get it. The vapour rising keeps the
air humid, and furnishes the dew that keeps all plant life comfortable
and happy even through the hot summer months.

Under the drift lie layers of stratified rock, and under these are the
granites and other fire-formed rocks, the beginning of those rock masses
which form the solid bulk of the globe. We know little about the core of
the earth, but the granites that are exposed in mountain ridges are
found to have a great capacity for absorbing water, so it is not
unlikely that much surface water soaks into the rock foundations and is
never drained away into the sea.

The water in our wells is often hard. It becomes so by passing through
strata of soil and rock made, in part, at least, of limestone, which is
readily dissolved by water which contains some acid. Soil water absorbs
acids from the decaying vegetation,--the dead leaves and roots of
plants. Rain water is soft, and so is the water in ponds that have muddy
basins, destitute of lime. Water in the springs and wells of the
Mid-Western States is "hard" because it percolates through limestone
material. In many parts of this country the well water is "soft,"
because of the scarcity of limestone in the soil.

I have seen springs around which the plants and the pebbles were coated
with an incrustation of lime. "Petrified moss" is the name given to the
plants thus turned to stone. The reason for this deposit is clear.
Underground water is often subjected to great pressure, and at this time
it is able to dissolve much more of any mineral substance than under
ordinary conditions. When the pressure is released, the water is unable
to hold in solution the quantity of mineral it contains; therefore, as
it flows out through the mouth of the spring, the burden of mineral is
laid down. The plants coated with the lime gradually decay, but their
forms are preserved.

There are springs the water of which comes out burdened wit