he waters that
remained in thousands of lakes great and small that now occupy the
region covered by the ice.

Ancient sea beaches mark the level of high water at the time that the
flood followed the melting ice. On the shores of Lake Champlain, but
nearly five hundred feet higher than the present level of the lake,
curious geologists have found many kinds of marine shells on a
well-marked old sea beach. The members of one exploring party in the
same region were surprised and delighted to come by digging upon the
skeleton of a whale that had drifted ashore in the ancient days when
the inland sea joined the Atlantic.

Lake Ontario's ancient beach is five hundred feet above the present
water-level; Lake Erie's is two hundred fifty feet above it; Lake
Superior's three hundred thirty feet higher than the present beach. No
doubt when the water stood at the highest level, the Great Lakes formed
one single sheet of water which settled to a lower level as the rivers
flowing south cut their channels deep enough to draw off the water
toward the Gulf. Lake Winnipeg is now the small remnant of a vast lake
the shores of which have been traced. The Minnesota River finally made
its way into the Mississippi and drained this great area the stranded
beaches of which still remain. The name of Agassiz has been given to the
ancient lake formed by the glacial flood and drained away thousands of
years ago but not until it had built the terraced beach which locates it
on the geological map of the region.

When the ice-sheet came down from the north it dragged along all of the
soil and loose rock material that lay in its path. With the boulders
frozen into its lower surface it scratched and grooved the firm bedrock
over which it slid, and rounded it to a smooth and billowy surface. The
progress of the ice-sheet was southward, but it spread like a fan so
that its widening border turned to east and west.

When it reached its southernmost limit and began to melt, it laid down a
great ridge of unsorted rock material, remnants of which remain to this
day,--the terminal moraine of the ancient ice-sheet. The line of this
ancient deposit starts on Long Island, crosses New Jersey and
Pennsylvania, then dips southward, following the general course of the
Ohio River to its mouth, forming bluffs in southern Ohio, Indiana, and
Illinois. The line bends upward as it crosses central Missouri, a corner
of Kansas, and eastern Nebraska, parallel with the cours