Page:The Journal of geology (IA journalofgeology11893univers).pdf/95

In an article on "Englacial Drift," in the July number of the American Geologist, my friend, Mr. Warren Upham, referring to my article in the first number of this Journal on the Englacial Drift of the Mississippi Basin, takes exception to the impression conveyed respecting his views in the matter of rising glacial currents. The present writer, he says, "several times speaks of the opinions of writers who believe in the considerable volume of the englacial drift, as if they supposed the glacial currents to move gradually upward from the ground to the ice surface. Such a supposition, however, seems to me quite untenable. Instead, in my own writings and those of most, if not all, of these authors, the exposure of the drift on the surface of the ice-sheet near its border, whence much of it was washed away to form the eskers, kames, and valley drift, is ascribed wholly to the superficial melting of the ice sheet, which is called ablation." I very much regret to have given expression, or to have seemed to have given expression, to the views of these writers in any other terms than they would themselves have chosen, and I cheerfully reproduce the corrective statement which Mr. Upham makes. Until my attention was called to the matter, no other interpretation of the views of these writers than that the supposed rising glacial currents moved on gradually to the surface of the ice occurred to me as possible, as no logical stopping place short of that suggested itself. I do not see any other consistent view now, but that does not affect the obligation to present accurately the views actually held. I hope these writers will credit me with attributing to them what seemed to be the most logical aspect of the hypothesis entertained by them. The supposed upward movement is attributed to differential motion