nt, produces the great power which is constantly forming sand-bars
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
with stone, and extending along the shore in a sufficient depth of water
to admit vessels riding easily at anchor under their lee. Many lives
and much property would undoubtedly be saved every year by such
constructions; for it is a difficult matter for a vessel to enter these
narrow rivers in a heavy gale of wind, and if she misses the entrance,
she is very likely to go ashore.

Another very important work to the navigation of the lakes is the
deepening of the channel in Lake St. Clair.

Between Lakes Huron and Erie lies Lake St. Clair, a shallow sheet of
water, some twenty miles in length, through which all the trade of the
Upper Lakes is obliged to pass. At the mouth of the river which connects
this lake with Huron, there