last twenty years, and that it
is now nearly equal in amount to the whole foreign trade of the country.
Before entering on the statistics of this trade, however, we will give a
brief description of the Lakes themselves.[A]

[Footnote A: We are indebted for our facts and details to Lapham's
_Wisconsin_, Foster and Whitney's _Report_, Agassiz's _Lake Superior_,
and works of similar character.]

Lake Superior, the largest expanse of fresh water on the globe, is 355
miles in length, 160 in breadth, with a depth of 900 feet. It contains
32,000 square miles of surface, which is elevated 627 feet above the
surface of the ocean, while portions of its bed are several hundred
feet below it. Its coast is 1500 miles in extent, with irregular, rocky
shores, bold headlands, and deep bays. It contains numerous islands, one
of which, Isle Royale, has an area of 230 square miles. The shores
of this lake are rock-bound, sometimes rising into lofty cliffs and
pinnacles, twelve or thirteen hundred feet high. Where the igneous rocks
prevail, the coast is finely indented; where the sandstones abound, it
is gently curved. Lake Superior occupies an immense depression, for
the most part excavated out of the soft and yielding sandstone. Its
configuration on the east and north has been determined by an irregular
belt of granite, which forms a rim, effectually resisting the further
action of its waters. The temperature of the water in summer is about
40 deg.

Lake Huron connects with Superior by the St. Mary's River, and is 260
miles long and 160 broad; its circumference is 1100 miles, its area
20,400. Georgian Bay, 170 miles long and 70 broad, forms the northeast
portion, and lies within British jurisdiction. Saginaw, a deep and
wide-mouthed bay, is the principal indentation on the western coast. The
rim of this lake is composed mostly of detrital rocks, which are rarely
exposed. In the northern portion of the lake, the trap-rocks on the
Canada side intersect the coast. The waters are as deep as those of
Superior, and possess great transparency. They rarely attain a higher
temperature than 50 deg., and, like those of Superior, have the deep-blue
tint of the ocean. The northern coast of Lake Huron abounds in clusters
of islands; Captain Bayfield is said to have landed on 10,000 of them,
and to have estimated their number at 30,000.

Lake Michigan, called by the early voyagers Lac des Illinois, is next in
size to Superior, being 320 miles in le