File:The soil, its nature, relations, and fundamental principles of management (1895) (14576667527).jpg

Identifier: soilitsnaturere00king (find matches)
Title: The soil, its nature, relations, and fundamental principles of management
Year: 1895 (1890s)
Authors: King, F. H. (Franklin Hiram), 1848-1911
Subjects: Soils
Publisher: New York, London : Macmillan and co.
Contributing Library: University of British Columbia Library
Digitizing Sponsor: University of British Columbia Library

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inter has not yet been learned, but during its prevalencethe snows piled upon the land until a mantle hundredsand perhaps thousands of feet in thickness overspreadthe whole area outlined above, while the general level ofthe ocean fell as its waters were drawn upon to feed theever-deepening snow fields as they spread over the north-ern continents of the Eastern and Western Hemispheresalike. As the specific gravity of ice varies between .917and .922-, the mean weight of a cubic foot will exceed 57pounds, and an ice sheet 10 feet in depth will press uponits bed with a weight exceeding 570 pounds to the squarefoot, while the burden imposed by 500 and 1000 feet ofice must exceed 28 and 57 thousand pounds to the squarefoot, or 198 and 396 pounds to the square inch respec-tively. What a mill for grinding rock into soil we havehere ! For its nether stone one-half or two-thirds of theNorth American continent, and for its upper one a blockof ice of corresponding size, five hundred to a thousand
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^ w oa OCO o 58 The Soil. and more feet thick, having its grinding face thickly setwith sand and gravel, and those same hard bowlders,large and small, which we now find strewn so thicklyover the surface and through the soil of this whole gla-ciated area, while the two faces were set against eachother with a pressure exceeding 200 to 400 pounds to thesquare inch and quite, probably double these amounts!With such a mill as this, set up under no other roofthan the dome of a cold arctic sky, and run incessantlyday and night, year in and year out, for centuries,numbered certainly by hundreds if not by thousands,a great work must have been accomplished. During all this time the great ice sheet was creepingslowly toward the south and southwest, its whole front,from the Atlantic to the Rocky Mountains, now advanc-ing a little and now retreating as variations in the rateof travel or the rate of melting occurred. Beneath thebottom of this slowly moving sheet of pressure-plasticice, which, with

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