NORTH America is divided into four distinct water systems by the Rocky Mountains, the Alleghanies, and a table-land which contains the great lakes, and separates the rivers that flow into the Arctic Ocean from those which go to the Gulf of Mexico. This table-land, which is a level, nowhere more than 1200 or 1500 feet above the surface of the sea, is the watershed of the Mackenzie, the Mississippi, the St. Lawrence, and of the rivers that flow into Hudson’s Bay. The St. Lawrence rises under the name of the St. Louis in 47° 43ʹ N. lat. and 93° W. long.; after joining the Lakes Superior, Huron, Erie, and Ontario, it issues from the last by the name of the Iroquois, and, expanding in its north-easterly course into Lakes St. Francis, St. Louis, and St. Peter, it is first known as the St. Lawrence at Montreal, from whence it runs north-east into the Atlantic, and ends in an estuary 100 miles wide. It has a basin of 297,600 square miles, of which 94,000 are covered with water, exclusive of the many lesser lakes with which it is in communication. North of the watershed there is an endless and intricate labyrinth of lakes and rivers, almost all connected with one another. But the principal streams of these Arctic lands are—the Great Fish River, which flows north-east in a continued series of dangerous and all but impassable rapids to the Arctic Ocean at Melville Strait; the Copper-mine River, of much the same character, which, after traversing many lakes, enters the Icy Sea at George the Fourth’s Gulf; and the Mackenzie River, a stream of greater magnitude, formed by the confluence of the Peace River and the Athabasca from the Rocky Mountains, which, after flowing north over 16 degrees of latitude, enters the Frozen Ocean in the Esquimaux country beyond the Arctic Circle. All these rivers are frozen more than half the year, and the Mackenzie, in consequence of its length and direction from south to north, is subject to floods like the Siberian rivers, because its lower course remains frozen for several hundred miles long after the upper part is thawed, and the water, finding no outlet, flows over the ice and inundates the plains.