UIHistories Project: A History of the University of Illinois by Kalev Leetaru
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Repository: UIHistories Project: Board of Trustees Minutes - 1871 [PAGE 190]

Caption: Board of Trustees Minutes - 1871
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182 tached from the parent rock in the form of soil. A soil thus formed must evidently be of the same nature as the rock from which it was derived. In this way, perhaps, the primeval soils of our planet were formed. At least, if the theory of La Place be true, glaciers can scarcely be supposed to have been concerned in their formation. Some rocks, like mica, slate and limestone, yield with comparative ease to atmospheric influences, while others, of firmer texture, withstand them a long time. In certain parts of Pennsylvania, the underlying rock is a kind of gneiss or mica slate, in others, it is limestone, and both, under the above mentioned influences, have furnished some of the most fertile soils of the State. In the same way, boulders and pebbles, particularly those of not very firm texture, gradually wear away and crumble to powder. Even the hard granitic rocks scattered here and there over the prairie, are slowly undergoing disintegration, and contributing their mite to the soil. But what is of special importance in an agricultural point of view, is, that to these same influences is due the further comminution of those particles that constitute our soils. As a rock exposes a vastly larger surface when broken into fragments than it did before, it is easy to see that the disintegrating influence of the atmosphere must be increased, provided the particles are all of the same kind, and the atmosphere has easy access to them. Hence, we see how intimately the mechanical treatment of soils is connected with atmospheric and climatic influences. If we would have a finely comminuted soil, and, therefore, the benefit of those ingredients essential to vegetable growth, we must expose it as much as possible to the disintegrating influences of the atmosphere. Another and very important agent in the formation of soils, is water. Most of our prairie creeks, especially after rains, are turbid with finely divided matter, held in mechanical suspension. This matter is carried into larger streams, and thence into still larger ones, until finally, it reaches the gulf, where it is spread out in the form of a plain or prairie to constitute the soil, perhaps, oi husbandmen of some future age. "Whoever has seen the great rivers of this mighty valley, thick, almost, with the material with which they are freighted, has seen illustrated on a grand scale, the transporting and leveling agency of water. It has been calculated that the mean annual amount of solid matter carried by the Mississippi to the gulf, is one cubic foot for every three thousand cubic feet of water, and some have estimated it considerably higher, making the total annual amount deposited in the gulf by the Mississippi alone, near four billion cubic feet, a mass equal to about one square mile in area, and 241 feet deep. Similar phenomena are