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Published online by Cambridge University Press: 01 May 2009
Some views in theoretical geology are held so vaguely that when one attempts to grasp them it is like clutching at shadows. To any one who will put his ideas into figures our thanks are therefore due.
1 Island Life, pp. 214—216. He says: “If therefore we take a wid ofthirty miles along the whole coast-line of the glohe as representing the area over which deposits are forming, corresponding to the maximum thickness as measured hy geologists, we shall certainly over—rather than under—estimatethe possihle rate of deposit. Now a coast-line of 100,000 miles with a width of 30 gives an area of 3,000,000 6quare mile on which the denuded matter of the whole land-area of 57,000,000 equare miles is deposited. As these two areas are as 1 t 19, it follows that deposition, as measured by maximum thickness, goes on at least nineteen times as fast as denudation—probably very much faster. But the mean rate of denudation over the whole earth is about one foot in three thousand years; therefore the rate of maximum deposition will be at least 19 feet in the same time; and as the total maximum thickness of all the stratified rocks of the globe is, according to Professor Haughton, 177,200 feet, the time required to produce this thickness of rock, at the present rate of denudation and deposition, is only 28,000,000 years.“