Excerpt from Man and the Glacial PeriodSee especially Chamberlin, in the American Journal of Sci ence, vol. Xlv, p. 192, Salisbury, in the American Geologist, vol. Xi, p. 18.Warren, Pa where, in an area which was affected by only the earliest glaciation, glacial deposits are found filling the rock channels of old tributaries to the Alleghany to a depth of from one hundred and seventy to two hundred and fifty feet, and carrying the preglacial erosion at that point very closely, if not quite, down to the present rock bottoms of all the streams. This removes from Professor Chamberlin a most important part of the evidence of a long interglacial period to which he had appealed, he having maintained* that the higher glacial gravels antedated those of the moraine-forming epoch by the measure of the erosion of the channel through the old drift and the rock, whose mean depth here is about three hundred feet, of which perhaps two hundred and fifty feet may be said to be be rock, adding that the exca vation that intervened between the two epochs in other portions of the Alleghany, Monongahela, and upper Ohio valleys is closely comparable with this.These observations of Mr. Leverett and myself seem to demonstrate the position maintained in the volume (page namely, that the inner precipitous rock gorges of the upper Ohio and its tributaries are mainly preglacial, rather than interglacial. The only way in which Professor Chamberlin can in any degree break the force of this discovery is by assuming that in preglacial times the present narrow rock gorges of the Alleghany and the Ohio were not continuous, but that (as indicated in the present volume on page 206) the drainage of various portions of that region was by northern outlets to the Lake Erie basin, leaving, on this supposition, the cm between two or three drainage areas to be lowered in gla cial or interglacial time.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.