Geology . Fig. 477.—Glacially faceted and scratched pebbles, remarkable for the number ofplaned faces, for the pronounced beveling, etc.; from the Illinois and Michigancanal, Chicago. The planes of cleavage are in such relations as to suggest that theywere developed by pressure from above. This is consistent with the THE PLEISTOCEXE OR GLACIAL PERIOD. 343 deposition of the foliated drift beneath a body of ice. The strati-fied drift shows by its structure that it was deposited by water. Thiswater doubtless sprang, very largely, from the melting of the ice. The structural relations of the two gr
Geology . Fig. 477.—Glacially faceted and scratched pebbles, remarkable for the number ofplaned faces, for the pronounced beveling, etc.; from the Illinois and Michigancanal, Chicago. The planes of cleavage are in such relations as to suggest that theywere developed by pressure from above. This is consistent with the THE PLEISTOCEXE OR GLACIAL PERIOD. 343 deposition of the foliated drift beneath a body of ice. The strati-fied drift shows by its structure that it was deposited by water. Thiswater doubtless sprang, very largely, from the melting of the ice. The structural relations of the two great types of drift will be referredto again, but a conception of these relations is necessary to an under-standing of the structure of the drift as a whole. Either type of thedrift may overlie the other, or the two may be interbedded; eithermay grade laterally into the other, either may abut abruptly againstthe other horizontally, or pockets of either may be enclosed in theother. The association of the t
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectgeology
