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Image 9 of The State College cadet, vol. 7, no. 2, November 1896

Part of The State College cadet

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l THE;CADET. 31 relation, in order to help the mind out in its effort to obtain an ade- · i quate comprehension of avast time magnitude. — Croll has suggested Q this illustration as a good one to convey to the mind some idea of what a million of years really is: _ "Take a strip of paper an inch broad, or more, and 83 feet 4 inches in length, and stretch it along the wall of a large hall, or round the walls of an apartment somewhat ove1· 20 feet square. Re- call to memory the days of your boyhood, so as to get some adequate conception of what a period of a hundred years is. Then mark off from one of tl1e ends of the strip one-tenth of an inch. The one- i tenth of the inch will then represent one hundred years, and tl1e A · entire length of the strip a million years. It is well worth making , the experiment, just in order to feel the striking impression that it _ l}·» ; produces 011 the mind " Or, suppose we take this as an illustration: The Kentucky river at High Bridge flows at the bottom of a gorge some 300 feet deep. \Ve know this gorge has been cut down to its present depth solely through the action of the river itself; and that, ` too, within a period of time geologically recent. How long has it taken the 1‘ZlV€1' to do this? A definite numerical answer to this question is not an easy one to give. The rate of river cutting is not uniform. Much depends upon the rate of land elevation. A river is like a saw ; to be kept at its wo1·k constantly the feed into it must be constant—that is, the bottom must be made to rise against it, as it were. If the reve1·se process—subsidence—take place, the river V will cease to cut, or may even begin to fill up its channel instead. But, suppose the action and the 1·ate has b€€l1 constant, resulting in the wearing away from the bed one—tenth of a foot in one hundred years; how long would you say it had taken for tl1e canon at High li Bridge to form? Would one million years seem too long or too short? By actual calculation, at such a constant rate, such a result could be easily accomplished in 300,000 years. It seems perfectly reasonable lf to conclude that the Kentucky 1·ivcr could have fo1·1ned its gorge li,} within one million years with considerable time to spare. Here is A if an instance of where we are liable to over, rather than under, esti- mat-e the time it has taken to accomplish a geological event; at least . · . , —

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