the rocks into the state of soil, which is continually
wearing away the material on the surface, or leaching it out through
the springs, is also at work in restoring the layer from beneath.

The greater part of the water which enters the soil does not
penetrate to any great depth in the underlying rocks, but finds its
way to the surface after no long journey in the form of small springs.
Generally those superficial springs do not emerge through distinct
channels, but move, though slowly, in a massive way down the slopes
until they enter a water course. Along the banks of any river, however
small, or along the shores of the sea, a pit a few inches deep just
above the level of the water will be quickly filled by a flow from
this sheet which underlies the earth. At a distance from the stream
this sheet spring is in contact with the bed rocks, and may be many
feet below the surface, but it comes to the level of the river or the
sea near their margins. Here and there the shape of the bed rocks,
being like converging house roofs, causes the superficial springs to
form small pipelike channels for the escape of their gathered waters,
and the flow emerges at a definite point. Almost all these sources of
considerable flow are due to the action of the water on the underlying
rock, where we shall now follow that portion of the crevice water
which penetrates deeply into the earth.

Almost all rocks, however firm they may appear to be, are divided by
crevices which extend from the soil level it may be to the depths of
thousands of feet. These rents are in part due to the strains of
mountain-building, which tend to disrupt the firmest stone, leaving
open fractures. They are also formed in other ways, as by the
imperfectly understood agencies which produce joint planes. It often
happens that where rocks are highly tilted water finds its way
downward between the layers, which are imperfectly soldered together,
or a bed of coarse material, such as sandstone or conglomerate, may
afford an easy way by which the water may descend for miles beneath
the surface. Passing through rocks which are not readily soluble, the
water, already to a great extent supplied with mineral matter by its
journey through the soil, may not do much excavating work, and even
after a long time may only slightly enlarge the spaces in which it
may be stored or the channels by which it discharges to the surface.
Hence it comes about that in many countries, even where