In the lower peninsula the arrangement of the bed rocks is simple, being like a nest , of basins, one within the other. At the centre the coal basin covers about one-fifth of the area. The minerals: of the other basins are various and widely distributed, among which are salt, clay, sand and gravels, liniesione and gypsum. At several points' 'are found mineral springs, where popular resorts have grown up to profit by the medicinal value of the waters; chief among these is' Mount Cletnens, near Detroit. The waters of four mineral springs are mar keted. The surface of the lower peninsula lends itself easily to agriculture, grazing, lum bering and manufacture. In general, it' is slightly undulating and but little raised alarm lake level. The peninsula is. divided into two portions, which, have a' few topographical dif ferences; the dividing line is the Grand-Maple Saginaw Valley, which, extending across it di agonally from the head of Saginaw Bay to Lake' Michigan, is nowhere above 100 feet high. North of this central plain rises a plateau, be tween 700 and 800 feet above the lakes, form ing the watershed between Lakes Michigan and Huron. At a point near Otsego Lake, this pla teaU reaches a height of 1,100 feet. On the north and northeast, outcrops of bed rock give the coast an abrupt and somewhat forbidding appearance. The portion of the peninsula south of the central plain rises rarely abOve 200 feet,.
broken by low conical hills, whose fertile in tervening dales form the courses of small streams. At the east, a morainal elevation, forming two watersheds, rises in Hillsdale County, 600 feet above the lakes, the highest point in this part of the State. The southeast ern shore is low and comparatively level. Along a largepart of the entire western shore of the peninsula, wind-blown sand dunes reach, in places, a height of 200 and 300 feet.
Off the shores of the two peninsulas lie some 200 islands within the State boundaries, the largest of which is Isle Royale, in Lake Supe rior. Others of the largest islands are: In Lake Superior—Grand Isle; in Lake Michi gan — Beaver, Fox and Manitou; and in Lake Huron— Sugar Island, Encampment Island, Drummond Island, Bois Blanc and Mackinac. The coolness of the summer climate of the up per Great Lakes has made of that region a de lightful watering place, particularly in the vicin ity of the Straits of Mackinac. Of the island resorts the most widely known is the picturesque Mackinac Island.
The three principal soil types of the two peninsulas are determined by the relative amount of sand, clay and lime. In the south ern peninsula, the soils vary from the light sandy loam of the north central plateau to heavy blue clay, on the Huron shore, and to the dark clay loam of southern Michigan. The
wide distribution of sand gives warmth to the soil, and its porosity prevents the drowning of crops; while the generous depth of the soil keeps it from drying out. There is little irre claimable marshland. In general, the soil is easy to work, presenting but little stony land like New England and very few barrens due to outcrops. The mixture of clay and sand makes a soil not too adhesive for the plow and one not easily washed full of gullies. The lime stone areas are specially fortified against de terioration through wasteful farming, and in many places there is an abundance of natural fertilizers. In the upper peninsula, in the west, the rocks are either barren or thinly covered, with an occasional fertile valley; in the east, the soil is of good depth and generally rich in a variety of mineral elements.
Drainage and Water Michigan has more than 5,000 interior lakes, mainly of glacial origin. Many of those near the shores, especially of Lake Michigan, were once a part of the Great Lakes. They vary in size from an acre to a thousand acres, covering in the ag gregate an area of 712,864 acres. Generally they have a border of woodland and sandy or muddy margins, with more or less vegetable and animal life. Many of these lakes are beau tiful pleasure resorts. Streams are fed by these lakes, which together with them form an equa ble system of drainage. The rivers, though nu merous, are relatively short and shallow, ow ing to the peninsular character of the State. Some have cut deep enough to form rapids, es pecially in the north, furnishing water power. Of the large power they could develop, 250,000 horse power is now furnished, mainly by the Saint Mary's, the Au Sable, the Menominee, the Saint Joseph, the Muskegon, the Grand. the Kalamazoo, the Huron and the Thunder Bay. In lumbering days, the Saginaw, the Mus kegon and the Menominee were chief among the many rivers for transportation of logs to mill. Aside from the strait-like Saint Marys, Saint Clair and Detroit rivers, Michigan streams are not navigable, except for the small est of river craft. Worthy of mention, besides the rivers named, are, in the lower peninsula. the Clinton, the Raisin, the Rouge, the Black and the Manistee; in the upper peninsula, the Taquamenon, the Carp, the Sturgeon, the Ma nistique, the Rapid, the Whitefish, Falls River and Dead River. The waters of these rivers are received by numerous bays and inlets which indent the shores; of these, the largest along the upper peninsula are Keweenaw, White Fish and the Big and Little Noquette bays; along the lower peninsula, the Grand and Little Traverse, the Thunder and Saginaw bays.