Huron, the second largest of the five great lakes on the frontier between the United States and Canada, is connected at the north-west by St Mary's River with Lake Superior, and through the strait of Mackinaw with Lake Michigan. On the south it has an outlet by way of the St Clair River. It is bounded on the W. and SW. by Michigan, and elsewhere by Ontario. The lake is divided into two unequal parts by the Cabot's Head peninsula and Grand Manitoulin island, the parts to the north being called North Channel and Georgian Bay. Its extreme length is 263 miles; its greatest breadth, exclusive of Georgian Bay, 105 miles; average breadth, 70 miles. The total area is 23,800 sq. m.; and its mean elevation is 5813/10 feet above sea-level, it being 20 1/2 feet below Lake Superior, and 8 4/10 above Lake Erie. Huron has a mean depth of about 250, and a maximum depth of 750 feet. There is an average difference between high and low water (due to winds and rain) of 1 3/10 foot. Huron, like the other lakes, is subject to violent storms. It contains about three thousand islands, nearly all Canadian. The waters are very clear and pure, and abound in fish. There are numerous good harbours and roadsteads, most of them on the Canadian side; at Sand Beach, Michigan, there is a harbour of refuge.