was so uniform and gentle as not to break or strongly bend them
from their original attitude.

The surface of some of these layers is ripple-marked. Hence the
sand must once have been as loose as that of shallow sea bottoms
and sea beaches to-day, which is thrown into similar ripples by
movements of the water. In some way the grains have since become
cemented into firm rock.

Note that the layers on one side of the valley agree with those on
the other, each matching the one opposite at the same level. Once
they were continuous across the valley. Where the valley now is
was once a continuous upland built of horizontal layers; the
layers now show their edges, or OUTCROP, on the valley sides
because they have been cut by the valley trench.

The rock of the ledges is crumbling away. At the foot of each step
of rock lie fragments which have fallen. Thus the valley is slowly
widening. It has been narrower in the past; it will be wider in
the future.

Through the valley runs a stream. The waters of rains which have
fallen on the upper parts of the stream's basin are now on their
way to the river and the sea. Rock fragments and grains of sand
creeping down the valley slopes come within reach of the stream
and are washed along by the running water. Here and there they
lodge for a time in banks of sand and gravel, but sooner or later
they are taken up again and carried on. The grains of sand which
were brought from some ancient source to form these rocks are on
their way to some new goal. As they are washed along the rocky bed