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16 THOMPSON'S COAST PILOT. the surplus waters poured from the vast basims of Superior, Michigan and Huron, flow across the plate of Erie into the deep bowl of Ontario. Lake Erie is reputed to be the only one of the series in which any current is perceptible. The fact, if it -- is one; is usually ascribed to its shallowness; but the vast vol- ume of its outlet--the Niagara River--with its strong current, is a much more favorable cause than the small depth of its water, which may be far more appropriately adduced as the reason why the navigation is obstructed by ace much more than either of the other great lakes. | The ascertained temperature in the middle of Lake Erie, August, 1845, was temperature of air 76° Fahrenheit, at noon; water at surface 73°--at bottom 53°. Lake Ontario, the fifth and last of the Great Lakes of Amer- ica, is elevated 234 feet above tide-water at Three Rivers, on the St. Lawrence; it is 180 miles long, 60 miles broad, 600 feet deep. | Thus basi succeeds basin, like the locks of a great canal, the whole length of waters from Lake Superior to the Gulf of St. Lawrence being rendered navigable for vessels of a large class by means of the Welland and St. Lawrence Canals--thus ena- bling a loaded vessel to ascend or descend 600 feet above the level of the ocean, or tide-water. Of these five great lakes, Lake Superior has by far the largest area, and Lake Ontario has the least, having a surface only of about one-fifth of that of Lake Superior, and being somewhat less in area than Lake Hrie, although not much less, if any, in the circuit of its shores. Lake Ontario is the safest body of water for navigation, and Lake Erie the most dangerous. The lakes of greatest interest to the tourist or scientific traveler are Ontario, Huron, together with Georgian Bay and North Channel, and Lake Superior. The many picturesque islands and headlands, together with the pure, dark green waters of the Upper Lakes, form a most lovely contrast during the summer and autumn months. | The altitude of the land which forms the water-shed of the Upper Lakes does not exceed from 600 to 2,500 feet above the level of the ocean, while the altitude of the land which torms