. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. 52. Theories of Glacier Motion. There are few subjects connected with the physics of the earth which have excited more interest than that of glacier-motion. The subject is one of exceeding beauty, and not without geological im- portance. Passing over several very ingenious theories which have now been abandoned, the first theory which was conceived in the true inductive spirit, and which explains the differential motion, is that of Prof. James Forbes. Viscosity Tlieory of Fortes. Statement of the Theory.
. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. 52. Theories of Glacier Motion. There are few subjects connected with the physics of the earth which have excited more interest than that of glacier-motion. The subject is one of exceeding beauty, and not without geological im- portance. Passing over several very ingenious theories which have now been abandoned, the first theory which was conceived in the true inductive spirit, and which explains the differential motion, is that of Prof. James Forbes. Viscosity Tlieory of Fortes. Statement of the Theory.—According to Forbes, ice, though appar- ently so hard and solid, is really, to a slight extent, a viscous body. In small masses this property is not noticeable, but in large masses and under long-continued pressure it slowly yields, and will flow like a stiffly viscous fluid. In large masses like a glacier, this steady, powerful press- ure is furnished by the immense weight of the superincumbent ice. Argument.—It is evident that this theory completely accounts for all the phenomena of glacier-motion, even in their minutest details. A glacier, beyond all doubt, moves like a viscous body, but it is still a question whether it does so by virtue of a property of viscosity. The. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original LeConte, Joseph, 1823-1901. New York : D. Appleton and Co.
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