SAINT LAWRENCE RIVER constitutes by far the largest body of fresh water in' the world. Including the lakes and streams, which it comprises in its widest acceptation, it covers, according to the lowest estimate, fully 73,000 sq.m.; and as nearly the whole of this area averages considerably more than 600 ft. in depth, the aggregate cannot rep resent less than 9,000 solid miles—a mass of water which would upward of 40 years to pour over the falls of Niagara, at the computed rate of a million cubic feet in a second. As the entire basin of this water-system falls short of 300,000 sq.m., the surface of the land is only three times that of the water.
This mighty artery of north-east America rises, under the name of the St. Louis, on the spacious plateau which sends fortlfalso the Mississippi toward the gulf of Mexico, and the Red river of the n. toward Hudson's bay—all three being said, in wet seasons, occasionally to mingle their floods. Lake Superior, the next link in the chain, finds its way to lake Huron through the rapid of St. Mary, which has been overcome by a ship canal on the right,•or American side. Below lake Huron, which receives lake Michigan from the s., the river St. Clair, lake St. Clair, the river Detroit, and lake Erie maintain pretty nearly the same level, till the river Niagara descends 334 ft. to lake Ontario, which is itself still 230 ft. above sea-level. From this, the last of the connected series of inland seas, issues the St. Lawrence proper, which, with a few comparatively insig nificant expansions, presents the character first of a river, and then of an estuary, down to the gulf. Between ink:: Ontario and the city of Montreal, which marks the head of
the navigation, there are various cataracts or rapids, which, besides having been grad ually ascertained to be more or less practicable, may be all avoided by means of canals on the British side. At about two-thirds of the distance from lake Ontario to the city of Montreal, the intersection of the parallel of 45° determines the point where the Sr. Lawrence, after having been an international boundary from the head, or nearly so, of lake Superior, becomes exclusively Canadian. Immediately above the island of Montreal, the St. Lawrence is joined by its principal auxiliary, the Ottawa, from the n.w.; and a little more than half-way between this confluence and Three rivers, the highest point of tidal influence, the Richelieu or Sorel, from the s., brings in the tribute of lake Champlain. Between Montreal and Quebec the St. Lawrence has recently been much deepened (see MoNTREAL). At Quebec, after a run of nearly 400 in. from lake Ontario, it steadily widens into an estuary of about the same length. The entire length, including the chain of lakes, is about 2,200 miles.
In connection with the improvements on itself and its affluents, the St. Lawrence offers to sea-going ships the noblest system of inland navigation in the world, embracing it continuous line of about 2,000 m.; its advantages, however, are. impaired by the severity of the climate, which binds it in the chains of winter at least five months in the year.