The cuesta begins where its determining limcstone begins, in west-central New York; there it separates the lowlands that contain the basins of lakes Ontario and Erie; thence it curves to the north-west through the province of Ontario to the belt of islands that divide1 Georgian Bay from Lake Huron; then westward throtigh the land-arm between lakes Superior and Michigan, and south-westward into the narrow points that divide Green Bay from Lake Michigan, and at last westward to fade away again with the thinning out of the limestone; it is hardly traceable across the Mississippi river.
So great, however, is the desire to shorten the time and distance necessary for the transportation of grain from Lake Superior to Montreal that an increasing quantity is taken by water as far as the Lake Huron and Georgian Bay ports, and thence by rail to Montreal.
On the Canadian side are Serpent river, Spanish river, French river, draining Lake Nipissing, Muskoka river, Severn river, draining lake Simcoe, and Nottawasaga river, all emptying into Georgian bay and North Channel, and Saugeen and Maitland rivers, flowing into the main lake.
Six passenger and freight steamship lines communicate with Cleveland, Buffalo, Sandusky, Detroit, Port Huron, Alpena, Mackinac, Georgian Bay and other points on the Great Lakes, and the city has 25 m.
The arrangement of the Great Lakes is thus seen to he closely synipathetic with the course of the lowlands worn on the two belts of weaker strata on either side of the Niagara cuesta; Ontario, Georgian Bay and Green Bay occupy depressions in the lowland on the inner side of the cuesta; Erie, Huron and Michigan lie in depressions in the lowland on the outer side.
The north-east shores of Lake Huron and its large expansion Georgian Bay are fringed with thousands of islands, mostly small, but one of them, Manitoulin Island, is 80 m.
In 1899 and subsequently surveys were made with a view to connecting the Georgian Bay through the intervening water stretches, with the Ottawa river system, and thence to Montreal.
Comparatively few have simple outlines and an unbroken surface of water, the great majority running into long irregular bays and containing many islands, sometimes even thousands in number, as in Georgian Bay and Lake-of-the-Woods.
The main lake reaches a depth of 802 ft.; Georgian bay shows depths, especially near its west shore, of over 300 ft.; North Channel has depths of 180 ft.
The construction of a ship canal to connect Georgian bay with Montreal by way of French river, Lake Nipissing and Ottawa river began in 1910.