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Show 1900] PHYSIOGRAPHY 13 drain an immense area in the interior of the continent, and their waters reach the Atlantic through the St. Lawrence. Other great inland bodies of water are Great Bear, Great Slave, and Athabasca lakes in the north, which empty into the Arctic by way of the Mackenzie River; lakes Winnipeg and Manitoba and Lake of ithe Woods, which drain into Hudson Bay, and certain desert lakes, such as Great Salt, which liave no outlets. NIn addition there are thousands of smaller lakes and ponds, particularly in the northern tier of states and in central Canada, the depressions which they fill having been formed for the most part by the grinding of the great Laurentian glacier. Generally speaking, the drainage of North America is into the Atlantic Ocean, and the larger part goes through the outlet of the great interior basin, the Mississippi, with its chief tributaries, the Missouri, Ohio, Arkansas, and Red rivers; or through the St. Lawrence, with its lake supply. The northern part of the basin is drained into the Arctic by the Mackenzie and into Hudson Bay by various streams, notably the Nelson River. East of the Appalachian barrier the narrow coastal plain is drained by a large number of streams of relatively short flow, of which the chief are the Kennebec, Connecticut, Hudson, Delaware, Susquehanna, Potomac, and James, all of which cut their way through the mountain ridges to reach the sea, and all of which played a part in determining early settlement |
