St Lawrence, a great river of North America, which, issuing from Lake Ontario, flows northeast 750 miles - part of the way forming the boundary between Canada and the United States - and falls into the Gulf of St Lawrence by a broad estuary. But in its widest acceptation the name includes the whole system of the Great Lakes and their connecting streams, with a total length from source to mouth of 2200 miles, and a drainage basin of 300,000 sq. m. The area of water-surface in the five lakes alone is 94,650 sq. m., and the system constitutes by far the largest body of fresh water in the world. This mighty artery of North-east America rises, under the name of the St Louis, on the spacious plateau which sends forth also the Mississippi towards the Gulf of Mexico, and the Red River of the North towards Hudson Bay. Lake Superior (602 feet above sea-level), the next link in the chain, finds its way to Lake Huron through St Mary's River, whose rapids have a fall of 20 1/2 feet. Below Lake Huron, which receives Lake Michigan from the south, St Clair River, Lake St Clair, Detroit River, and Lake Erie maintain pretty nearly the same level (there is a fall of some 8 feet, however, in Detroit River) till the river Niagara descends 326 feet to Lake Ontario, which is itself still 247 feet above the sea-level. The St Lawrence proper, with a number of lake-like expansions (such as the Lake of the Thousand Isles, of St Francis, St Peter, &c), presents the character first of a river, and then of an estuary, down to the gulf. Prior to 1858 only vessels drawing not more than 11 feet of water could pass up above Quebec; but since then a channel has been made in the shallow parts of the river, 300 feet wide, and so deepened that practically the largest ocean-.steamers can now pass tip to Montreal. Between Lake Ontario and Montreal there are several rapids, which, however, may be all avoided by means of canals. Immediately above the island of Montreal the St Lawrence is joined by its principal auxiliary, the Ottawa (800 miles), from the north-west; and a little more than half-way between this confluence and Three Rivers, the highest point of tidal influence, the Richelieu from the south brings in the tribute of Lake Champlain. Other principal tributaries are the St Maurice (400 miles), the Saguenay (100), and the Batiscan (50). Steamers may now by help of the canals convey their cargo from Liverpool to Duluth at the far end of Lake Superior without breaking bulk. The width of the St Lawrence varies from less than 1 to 4 miles; the estuary at its mouth is above 100 miles across. During winter the river is frozen over and navigation closed.
The Gulf of St Lawrence, an inlet of the North Atlantic, washes Newfoundland, Quebec, New Brunswick, and Nova Scotia. It has three communications with the ocean - the Strait of Belleisle, between Newfoundland and Labrador; the Gut of Canso, between the island of Cape Breton and Nova Scotia; and a far wider passage than either, with the island of St Paul in the middle, between Cape Breton and Newfoundland. It narrows, at the west end of Anticosti, into the estuary of the St Lawrence River. Besides Anticosti, St Paul's, and Prince Edward's, this arm of the sea contains many other islands, rendered dangerous to shipping by the fogs and the uncertain currents. Both Gulf and River are celebrated for their fisheries.