The present is a opportunity to cor rect a prevalent error. Lake Superior has been called the American Caspian, and very frequently stated to be equal or even more extensive than the Caspian. But these comparisons are very errone ous; the Caspian is 690 miles from south to north, and the mean width at least 180 miles, giving an area of 124,200 square miles; or upwards of four fold more extensive than is lake Superior. In re ality the whole five great lakes of Canada, and all the intermediate land taken together, but little ex ceeds the surface of the Caspian; and the actual water surface of the five Canadian lakes is to that of the Caspian as one to three very nearly.
The surface of lake Superior is elevated above the Atlantic tides 641 feet, but the utmost depth sinks below the ocean level, and of course if a strait level with the ocean connected it with the lake, the latter would still exist as an inland sea.
The immense depth of the Canadian lakes, ex cept Erie, is indeed amongst the most extraordinary facts in their natural history. Lake Superior is perhaps the deepest of the three higher lakes, but each admits the navigation of the largest vessels.
Similar to the Caspian, the lakes of Canada have shores very deficient in harbours; and lake Superior in particular has immense walls of rock stretch ing along much of its border.
The enormous mass of water from Superior pass es over what has been very erroneously called the falls of St. Mary, but which is in reality not a very steep cataract, and is passable with boats. The en tire fall determined by general Gratiot is 22 feet 10 inches. The strait of St. Mary if measured from the lower end of St. Joseph's island into the open water of lake Superior, is about seventy miles in direct length. The real narrows at the cataract, where Fort Brady now stands, is at N. lat. 3 C. Long. 18' W. from the meridian of Washington city.
From the geographical position and the long and intense frosts so near the eastern side of a large continent, the upper lakes of Canada would be an nually frozen in winter, if that phenomenon was not prevented by their prodigious depth. Their bays and rivers are annually frozen, in fact; but the great mass and depth of the open lakes prevent the formation of solid, compact, and passable fields of ice. DARBY.