HISTORICAL GEOLOGY OF MICHIGAN. 5 



this movement, on the eastern side of the State, seemed to have been from 

 the northeast; on the western side, it may have been more from the north. 

 The erosion of the continental glacier gave origin to the boulders and finer 

 materials which occupy the preseuL surface, and its movement transported 

 them southward. By such action were deepened, if not originated, the val- 

 leys of Lake Erie, Lake Huron, Saginaw Bay, and Lake Michij^an, with its 

 appended bays. This action, combined with the strike of the underlying 

 strata, has determined those trends in the physiographic features of the 

 State, which we have designated as the '* Diagonal System." 



In due time a change of climate, dissolving the glacier, originated torrents 

 of water, which imparted an imperfect stratification to the superficial portion 

 of the drift materials. There was, perhaps, a subsidence, which buried the 

 whole State again beneath the waters of the ocean. Whether this were so 

 or not, the great valleys excavated by Mesozoic and glacier agencies, were left 

 filled with the water which either was, originally, or in time became fresh 

 water. The breadth of the great lakes exceeded vastly their present dimen- 

 sions. Lakes Erie, St. Clair, and Huron were one. Through Saginaw Bay 

 and the valley of the Grand River, Lake Huron connected with Lake Michi- 

 gan. The latter spread over the prairie region of Illinois. By the removal 

 of the eastern barriers, the lakes were slowly drained to their present dimen- 

 sions. 



The surface of the Lower Peninsula was, at first, dotted with almost num- 

 berless small lakes. Many of these, by filling with sediments, marl and peat, 

 became converted into marshes or even meadows and arable lands; and the 

 remainder of them are undergoing the same process. 



It is likely that in America, as in Europe, man made his appearance while 

 the dissolution of the glacier was in progress. We have, at least, some evi- 

 dence of his presence in Illinois, while the prairies were a lake bottom. 



Whatever may be the conclusion as to the correctness or propriety of the 

 assumptions embodied in the foregoing extract, they surely possess the merit 

 of accounting very perfectly for the constitution, as well as for the present 

 condition of Michigan soils, as compared with those of the regions further 

 west and south. 



While the mineral constituents so bountifully supplied to the soils of 

 the Peninsular State by the disintegration of its rocks, have, under the 

 favoring influences of surrounding waters and tempered breezes, built 

 up its soils from the debris of the growth and decay of dense forests, pre- 

 paring them by both original consitution and subsequent addition and ameli- 

 oration, to more fully meet the varied needs of modern agriculture and hor- 

 ticulture. On the other hand, the naturally even richer soils of the adja- 

 cent regions, lacking these favoring lacustrine influences, and subjected, 

 through uncounted ages, to the influence of constant decay, and to annual visi- 

 tations of prairie fires, have been kept open to the free sweep of winds, with a 

 consequently rapid evaporation of moisture, accompanied by more severe 

 extremes of heat and cold, circumstances which seem naturally and fully to 

 account for the propagation eastward of the dryer climates, and the treeless 

 condition of the great western plateau. 



The highest lands in the southern portion of the Lower Peninsula occur 

 in the town of Somerset, in Hillsdale county, where the elevation above the 

 level of the surrounding lakes reaches six hundred and thirteen feet. North 

 of this, and extending from the Saginaw and Bad rivers across to those of 



