The requisites to the fertility of the soil, while partly organic, are largely inorganic. The great bulk of it is composed of mineral substances derived from rock formations, 53 and of these the rocks of the southern peninsula furnished a large proprotion of all but the alumina and potash, 54 which were derived from the mica and feldspar in the pre-Cambrian formations. Much of the sand came from the latter source-the quartzites, granites, syenites, and gneissoid rocks of regions north of the peninsula-traceable even to rocks as far north as Hudson Bay.

The transporting agents were the ancient continental glaciers. While there appears to be little agreement as to the cause, advance and retreat of these great ice masses, geologists concur as to the fact of the phenomenon, and that it affected in varying degree all of the northern continents.55 As they advanced, scouring and grinding the rocks of the lower peninsula, the soil products were thoroughly mixed and spread in varying thickness over a surface worn down and smoothed.

The thickness of these glacial deposits average about three hundred feet. The greatest depth is not known. 53. Silica, alumina, lime, magnesia, oxide of iron, oxide of magnesia, potash, soda, chlorine, sulphuric acid, carbonic acid.

54. Resources of Michigan (Lansing, 1893), 40.

55. For theories of the advance and cause of the ice age, see Lane, "The Surface Geology of Michigan," in Mich. Geol. Survey Rep. (1907), 98-101. There is a good outline for the southern part of the peninsula in Leverett, "Glacial Geology of Southeastern Michigan," in U. S. Geol. Survey (1899), Monograph XXXVIII, 339-379, 386-406, 432-450. A good brief bibliography of the glacial history and deposits of Michigan is given by Leverett in the Sixth Rep. Mich. Acad. of Science (1904), 100-110.

Deep well borings have penetrated sixteen hundred feet and it is thought probable that they may reach an extreme depth of two thousand feet. 56 It would be expected from what has been said of the greatest elevation of the bed rocks, the soil would be thinnest on the glacial moraines, and that is found to be true; for example, in parts of Jackson and Hillsdale counties. 57

The fineness of these soils, their mechanical composition, is due obviously to forces introduced by glacial action, varying with the degree to which the rocks were broken up; and to the same agencies is due their mechanical distribution. The United States Bureau of Soil's scheme of soil classification for Michigan, based on mechanical composition, shows twenty varieties of soil varying from fine clay to the coarsest gravel, and the Michigan geological survey for 1907 has mapped the distribution of these under six principal groups. 58 56. Mich Geol. Survey Rep. (1907), 101. 57. Sixth Rep. Mich. Acad. of Science, 103, 104. A special study has been made of soil depths in Monroe County, in Mich. Geol. Survey Rep., VII, 192 (Contains contour map of various depths). The average thickness of the drift in the lower peninsula is about 300 feet. See Leverett's discussion in Mich. Geol. and Biol. Survey, Pub. 9, Geol. Series 7 (1912), 19-20.

58. For brief description of the soils of the State and their adaptibility to agriculture, see Mich. Geol. Survey Rep. (1907), 115-119. Accompanying this is a soil map of the State prepared by J. F. Nellist (in pocket), based upon the twenty fine-soil divisions made by the U. S. Dept. of Agriculture, Bureau of Soils. The latter service has prepared soil maps of the vicinities of Owosso, Allegan, Alma, Pontiac, Saginaw and Cass counties. On this map, the glacial outwash aprons (represented by bright yellow) indicate the better class of sandy lands, fine sandy soils resulting directly from glacial over-wash or deposited in glacial lakes. They are widely distrib

The general advantages of these soils are many and important. Some of them will be already apparent. Their great variety in both chemical amd mechanical composition and the comparatively wide distribution. of most of them, laid the basis for a wide range of flora and of rural industries. The wide distribution

uted but are most extensive in the south and west of the peninsula and along the crest of the southeastern divide above the bed-rock sandstone. The poorer sandy lands (light yellow), due mainly to glacial drainage, are found over the sandstone beds along the shore of Lake Michigan, also in narrow bands through the heavy clay. along the eastern shore and around the head of Saginaw Bay. The soils of greatest extent are those of morainal origin. Both of the morainal soils cover a somewhat rolling and stony surface. That in which clay predominates (solid red) is distributed mainly in wide. bands which mark the successive projections of the Saginaw and Huron ice lobes into the interior. The soil of similar character (stippled red) in which sand predominates is of looser texture and covers wide areas over the southern and central portions of the peninsula. The till plains (blue) have more clay than the morainal soils. and cover a less hilly, or even level, surface, lying between the moraines. They are a fine sandy clay and cover portions of the southern limestone areas, but they are most abundant between the moraines southwest of Saginaw Bay. Along the eastern shore, covering a large part of Monroe, Wayne, Macomb and St. Clair counties and reaching inland from Saginaw Bay far south into Shiawassee County, is a stiff lake clay (green) representing the ancient glacial lake bottom over limestone areas. This is one of the most fertile soils of the peninsula, and was the first with which settlers from the East came in contact. Its heavy forests of ash and elm seriously. checked its settlement. See also map (new edition of Lane's map of 1907) of a somewhat more minute classification, in Mich. Geol. and Biol. Survey, Pub. 9, Geol. Series 7 (1912), opposite p. 12. Detailed data is given in the same volume (pp.87-140), by counties, arranged alphabetically, showing area, swamp and lake sections, and the predominant soils in each township.

and abundant proportions of sand, which gains heat rapidly, gives warmth to the soil, moderated by the presence of clay. Mositure is well proportioned. The porosity of the sand prevents the drowning of crops, and the depth of the soil together with the clay keeps it from drying out. There is little irreclaimable marshland. In general the soil is easy to work, for the assorting action of glacial lakes left the finer materials on the surface. With a few exceptions it is not stony like New England soil, and there are 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 limestone areas are specially fortified against deterioration through wasteful farming, and in many places there is an abundance of natural fertilizers.

Important to these soils is their drainage and their water supply, which depends largely upon the topography of the peninsula. The striking similarity between certain topographic features of the whole of the surrounding region suggests a common origin in some force that operated more widely than in Michigan only. A common feature is seen, for instance, in the general direction of the axis of the Saginaw River and Bay, the St. Lawrence River and Gulf, the Maumee River and the Bay and the Fox River and Green Bay. This long ago observed by Alexander Winchell was designated by him the "diagonal system" in the topography of this region. The axes appear to have been determined by the direction in which the ice lobes were projected, in combination with the strike, or angle, of

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the strata over which they passed. Where the bedrocks were sufficiently consolidated to offer effective resistance to the force of the ice, the diagonal direction of the surface features suffered modification; for example, the Michigan shore of Lake Michigan now runs approximately north and south. Along part of the eastern shore the underlying trend caused conjointly by these forces has been concealed by postglacial deposits; the St. Clair and Detroit rivers running over these southward cause the peninsula in this part to have a nearly uniform width.

By the original position of the ice lobes, by the depth of the great lake basins and by the gradual recession of the glacial waters, the peninsula was left with an area large enough to insure a variety of settlement and a pioneer period of long duration. Roughly, the peninsula has an area of two hundred by three hundred miles, with the longer axis north and south.60 That portion of it which lies south of the latitude of the head of Saginaw Bay, which alone received settlers by 1837, about equals the combined areas of Vermont, Massachusetts and Connecticut. The average width of this part of the peninsula is about one hundred and ninety 59. See Winchell's formula for the relation of the glacial and stratigraphic forces in the topography of the region, in Tackabury's Atlas, 14, and a more extended discussion in Amer. Jour. of Science, 3rd ser., VI, 36-40. The "diagonal system" in Monroe County is discussed in Mich. Geol. Survey Rep., VII, 118.

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60. The extreme length of the lower peninsula is 277.09 miles; the extreme width is 197.057 miles. (Tackabury's Atlas, 9).

61. Montcalm County was organized in 1850 (Session Laws, 121), with a population of about nine hundred (U. S. Census, 1850, 893).