_Maniton Island_ is situated near the eastern coast of Lake Michigan; it is six miles long and four wide, and is held sacred by the Indians. The _Castor Islands_ are a chain of islets, extending from Grand Traverse Bay nearly across the lake; they are low and sandy, but afford a shelter for light boats in their passage to Green Bay. _Grosse Isle_ is a valuable alluvion of several thousand acres, being five miles long, and from one to two wide. GENERAL REMARKS ON ISLANDS. It has been well observed, that a large island is a continent in miniature, with its chains of mountains, its lakes, rivers, and not unfrequently its surrounding islets. The smaller islands are found single, or in groups. Among the low or flat islands, there are some which are only banks of sand, scarcely raised above the surface of the water; sometimes they consist of masses of shells or petrifactions, as the Isles of Lachof to the north of Siberia, which are nothing but masses of ice, sand, and the bones of the mammoth. The Pacific contains a great many islands formed of coral reefs, which are sometimes covered with sand, and afford nourishment to a few plants. Among the more elevated islands we find very many which owe their foundation, in a great measure, to volcanic agencies. Submarine islands, as they have been sometimes called, or immense sand-banks, covered with shoal water, are not unfrequent. Chains of islands in the neighborhood of continents seem to be often formed by the action of the waters washing away the less solid parts, which once occupied the spaces between the mountains and rocks. In this manner were probably formed the islands along the coast of the United States, which still appear above the surface of the waves. One of the chief advantages that islands derive from their situation is, that the climate is generally rendered mild and salubrious, from the vapors of the surrounding sea, which generally moderate the violence of heat and cold, both of which are sensibly less than on the continent in the same latitude. Another advantage is found in their accessibility on every side, by which islands are open to receive and export commodities, and at times when the ports of the continent are closed. An island has on all sides the most extensive and effectual frontier, subsisting forever without repairs and without expense; and, which is still more, derives from this very frontier, a great part of the subsistence of its inhabitants, and a valuable article in its commerce, from fisheries.