the world.

The lakes afford a navigable water-way which, measured due east and
west, aggregates nearly six hundred miles. This route is interrupted at
Niagara Falls and at St. Mary's Falls, between Lake Superior and Lake
Huron. On the Canadian side, Welland Canal, Lake Ontario, and the St.
Lawrence connect Lake Erie with tide-water. In the United States the
Erie Canal connects the lake with the Hudson River and New York Bay.

From the head of Lake Superior railway routes of minimum grades--the
Great Northern and the Northern Pacific[51]--cross the continent to
Puget Sound, the best harbor approach to the Pacific coast of the
American continent. The harbors of Puget Sound, moreover, are materially
nearer the great Asian ports than any other port of the United States.
The level margins of these lakes are roadbeds for many miles of railway
track; in many instances the railways are built on the tops of terraces
that once were shores of the lakes.

[Illustration: DULUTH]

_Duluth_, at the head of Lake Superior, became commercially important
when the St. Mary's Falls Canal was completed. Much of the tremendous
tonnage of freight passing through the canal is assembled at this place.
The freight shipped consists mainly of farm products collected from an
area reaching as far west as the Rocky Mountains. There is also a
considerable shipment of iron ores obtained near by. _Buffalo_, at the
lower end of Lake Erie, owes its activity to the trade in lumber, grain,
and other farm products that come from Western lake-ports. It is the
eastern terminus of the lake-commerce and the western terminus of the
Erie Canal.

_Chicago_, at the head of Lake Michigan, has a very heavy lake-trade.
The mouth of Chicago River, the natural harbor of the city, has been
improved by a system of basins and breakwaters. The river itself has
been converted into a ship and drainage canal that is connected with the
Illinois and Mississippi Rivers. It is now an outlet instead of a feeder
to the lake, and the city built about old Fort Dearborn has become the
greatest railway centre in the world.

[Illustration: GENERAL VIEW OF LOCKS AND CANAL, SAULT STE. MARIE]

_Milwaukee_ has a situation in many ways resembling that of Chicago,
its harbor being the mouth of Milwaukee River. Like Chicago, it owes its
importance to its lake-trade. _Detroit_ (with _Windsor_, Ont.) owes its
growth partly to its strategic position on the strait connecting Lake
Huron and L