Largest fresh-water lake on the globe, lies between the United States and Canada, the boundary line passing through the centre; area, 31,200 sq. m., almost the size of Ireland; maximum depth, 1008 ft.; St. Mary's River, the only outlet, a short rapid stream, carries the overflow to Lake Huron; receives upwards of 200 rivers, but none of first-class importance, largest is the St. Louis; is dotted with numerous islands; water is singularly clear and pure, and abounds with fish; navigation is hindered in winter by shore-ice, but the lake never freezes over.