Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/20

xvi F³.

“There were also temporary drains through the pre-glacial divide during the Ice age: on the west, through the Maumee into the Wabash; on the east, through the Mohawk into the Hudson; and five on the south, as shown in I3, page 373.

“What caused these immensely thick deposits (fills as I have called them) at points which are now the summit divides of modern water-ways, and which always hold either lakes or swamps of considerable dimensions? May it be that, when a southern under-ice drainage had become established, there was a middle ground between the diverging north and south currents where there was little movement in the water, and where all the materials dropped by the ice remained comparatively undisturbed, and thus accumulated rapidly and built up the barrier? At any rate it seems as if quiet conditions prevailed when the barriers were being completed, for the surface deposits always consist of still-water materials.

“The subject is so broad and there are so many complex questions connected with it, that I feel incompetent to deal even with those facts and figures already accumulated. But I enjoy the study, and shall continue to investigate for my own personal gratification, whether it be of any interest to the public at large or not.”

There is a danger to be encountered in this study of glacial topography which must not be ignored—the danger of confounding the old topography with the new; the danger of ascribing to glacial waters the channeling of the great