and shoals at all the harbor-entrances on our extensive lake-coasts. To
counteract the effect of this great power, upon a given point, is what
we have chiefly to contend for in planning the harbor-piers for all the
lake-ports intended to be improved. The point which an engineer first
aims at, in undertaking to plan any of these harbor-works, is to
ascertain as nearly as possible the direction and force of the
prevailing winds."

The length of the Chicago piers is as follows:--North pier, 3900 feet
long, 24 feet wide; south pier, 1800 feet long, 24 feet wide; and they
are placed 200 feet apart.

Harbors of this kind have been constructed at Chicago, Waukegan,
Kenosha, Racine, Milwaukee, Sheboygan, Manitoowoc, Michigan City, and
St. Joseph, on Lake Michigan; at Clinton River, on Lake St. Clair; at
Monroe, Sandusky, Huron, Vermilion, Black River, Cleveland, Grand River,
Ashtabula, Conneaut, Erie, Dunkirk, and Buffalo, on Lake Erie; at Oak
Orchard, Genesee River, Sodus Bay, Oswego, and Ogdensburg, on Lake
Ontario.

For Lakes Huron and Superior it is believed that no appropriations have
been made, the scanty population of their shores not seeming as yet
to demand it, and those two lakes having in their numerous groups of
islands more natural shelter for vessels than Michigan or Erie.

Besides these river-harbors, Col. Graham recommends to Government the
construction at certain points on the lakes of sheltered roadsteads, or
harbors of refuge, to which vessels may run for shelter in bad weather,
when it may be difficult or dangerous to enter the river-mouths. These
are proposed to be made by building breakwaters of crib-work, loaded