quantities in the coating, and continually in slow motion, the
gas-charged water takes a host of substances into solution, and brings
them into a condition where they may react upon each other in the
chemical manner. These materials are constantly being offered to the
roots of plants and brought in contact with the underlying rock which
has not passed into the state of soil. The changes induced in this
stony matter lead to its breaking up, or at least to its softening to
the point where the roots can penetrate it and complete its
destruction. Thus it comes about that the water which to a great
extent divides 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