slackening speed makes even the sand too heavy a weight, and that in
turn falls to line the river-bed, while the now broad and placid
stream carries only the finer particles of mud suspended in its
waters. Soon it reaches the ocean, and the flow being there checked by
the incoming ocean-tide, even the mud can no longer be held up, and it
also sinks slowly in the shallows near the shore, forming sometimes
broad mud-banks dangerous to the mariner.

This is the case only with smaller rivers. Where the stream is
stronger, the mud-banks are often formed much farther out at sea; and
more often still the river-detritus is carried away and shed over the
ocean-bed, beyond the reach of our ken. The powerful rush of water in
earth's greater streams bears enormous masses of sand and mud each
year far out into the ocean, there dropping quietly the gravel, sand,
and earth, layer upon layer at the bottom of the sea. Thus pulling
down and building up go on ever side by side; and while land is the
theatre oftentimes of decay and loss, ocean is the theatre oftentimes
of renewal and gain.


Did you notice the word "sediment" used a few pages back about the
settlement at the bottom of a medicine-vial?

There is a second name given to the Stratified Rocks, of which the
earth's crust is so largely made up. They are called also _Sedimentary
Rocks_.

The reason is simply this. The Stratified Rocks of the present day
were once upon a time made up out of the sediment stolen first from
land and then allowed to settle down on the sea-bottom.