e of the
Missouri.

As the ice-sheet melted, boulders were dropped all over the Northern
States and Canada. These were both angular and rounded. In some places
they are scattered thickly over the surface and are so numerous as to be
a great hindrance to agriculture. In many places great boulders of
thousands of tons weight are perched on very slight foundations, just
where they lodged when the ice went off and left them, after carrying
them hundreds of miles. Around them are scattered quantities of loose
rock material, not scored or ground as are those which were carried on
the under-surface of the glacial ice. These unscarred fragments rode on
the top of the ice. They were a part of the top moraine of the glacial
sheet.

The finest material deposited is rock meal, ground by the great glacial
mill, and called "boulder clay." It is a stiff, dense, stony paste in
which boulders of all sizes, gravel, pebbles, and cobblestones are
cemented.

The "drift" of the ice-sheet is the rubbish, coarse and fine, it left
behind as it retreated. Below the Ohio River there is a deep soil
produced by the decay of rocks that lie under it. North of Ohio is
spread that peculiar mixture of earth and rock fragments which was
transported from the north and spread over the land which the ice-sheet
swept bare and ground smooth and polished.

The drift has been washed away in places by the floods that followed the
ice. Granite domes are thus exposed, the grooves and scratches of which
tell in what direction the ice flood was travelling. Miles away from
that scored granite, but in the same direction as the scratches,
scattered fragments of the same foundation rock cover fields and
meadows. Thus, much of the drift material can be traced to its original
home, and the course of the ice-sheet can be determined. Many immense
boulders the home of which was in the northern highlands of Canada rode
southward, frozen into icebergs that floated in the great inland sea.
Great quantities of debris were added to the original glacial drift
through the agency of these floating ice masses, which melted by slow
degrees.

FOLLOWING SOME LOST RIVERS

What would you think if the boat in which you were floating down a
pleasant river should suddenly grate upon sand, and you should look over
the gunwale and find that here the waters sank out of sight, the river
ended? I believe you would rub your eyes, and feel sure that you were
dreaming. Do not all ri