Geology . s with stratification(Fig. 473). The various lines of evidence which have led to the gen-eral acceptance of the glacial theory, have to do with (1) the drift,(2) the surface of the rock which underlies it, and (3) the relationsof the drift to its bed. Some of the principal considerations are thefollowing:2 1 Chamberlin, Jour, of Geol., Vol. I IT, 1895. 2 The phenomena pointing to the glacial origin of the drift have become so fa- ,,.,s GEOLOOY, (1) The constitution of the drift. One of the striking character-istics of the drift, taken as a whole, is its heterogeneity, both physical a
Geology . s with stratification(Fig. 473). The various lines of evidence which have led to the gen-eral acceptance of the glacial theory, have to do with (1) the drift,(2) the surface of the rock which underlies it, and (3) the relationsof the drift to its bed. Some of the principal considerations are thefollowing:2 1 Chamberlin, Jour, of Geol., Vol. I IT, 1895. 2 The phenomena pointing to the glacial origin of the drift have become so fa- ,,.,s GEOLOOY, (1) The constitution of the drift. One of the striking character-istics of the drift, taken as a whole, is its heterogeneity, both physical and lithological. It is made up, al one extreme, of huge bowlders(Figs. 171 and 17.)), and at the Other of impalpable earthy these extremes there are materials of all sizes, and the pro-portions of coarse and fine are subject to the greatest variations. Coarsematerials are, on the whole, most abundant in regions of rough topog-raphy where the underlying formations are resistant, and in the lc. Fig. 472.—A section of stratified drift. of such situations. Fine materials, on the other hand, are most abun-dant where the underlying formations, and especially the neighbor-ing formations in the direction whence the ice came, are weak. The miliar that it is unnecessary to give extended references to the literature of the sub-ject. They were emphasized in many of the early publications concerning the drift,The striae and other scorings of the ice. are elaborated in the 5th Ann. Kept. U. SGeol. Surv. The study of the drift from the standpoint of genesis is given in theJour of Geol.: Vol. II, pp. 708-724, and 837 851, and Vol. Ill, pp. 70-97, and inGlacial Geology of New Jersey, pp. 3-33. The geological reports of all the statesaffected and of Canada contain descriptions of the phenomena. THE PLEISTOCENE OR GLACIAL PERIOD. 339 fine material of the drift is made up, in large part, of the same mate-rials as the gravel and bowlders, but of these materials in a finerstate of s
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