198 THE ICE AGE IN NORTH AMERICA. 



Mountains, northeast of the Susquehanna Gap at Pittston, 

 showed distinct signs of glaciation on their highest summits, 

 which are from 2,000 to 2,200 feet above tide. This would 

 give a depth of 1,500 feet in the Susquehanna Valley in that 

 neighborhood.* 



The most formal attempt to estimate from known data 

 Uie depth of the ice near its ancient margin is that by Pro- 

 fessor J. C. Smock, in a paper f before the American Asso- 

 ciation for the Advancement of Science at Montreal. Pro- 

 lessor Smock finds definite evidence in northern New Jersey 

 of a depth of only about seven hundred feet to the ice, 

 though it is impossible to say that it was not more. For ex- 

 ample, the highest points of Schooley's Mountain table-land 

 consist of moraine hills from twelve to thirteen hundred feet 

 above tide, while the Musconetcong Yalley to the west, which 

 the ice had to fill before it surmounted the elevations indi- 

 cated, is seven hundred feet lower, showing that the ice must 

 at that point have been in the neighborhood of a thousand 

 feet in thickness. Professor Smock was also the first one to 

 ascertain that Pocono Mountain, in Monroe county, Pa., 

 showed signs of glaciation up to a height of over two thou- 

 sand feet. From the study of the glacial phenomena of that 

 region, Professor Smock correctly infers that " the inclination 

 of the continental ice-sheet of the Glacial epoch was not uni- 

 form. The rise was probably steep near the margin. . . . 

 Thus, near Feltville and Summit, the drift-covered Spring- 

 field Mountain, which is about a mile north of the line, is 

 nearly six hundred feet high. The high drift-hills near 

 Mount Hope (960 feet) [also] show a great thickness near 

 the margin. . . . Northward the angle of the slope dimin- 

 ished, and the glacier surface approximated to a great level 

 plain. The distance between the high southwestern peaks 

 of the Catskills and Pocono Knob in Pennsylvania is sixty 



* " The Thickness of the Ice in Northeastern Pennsylvania during the Gla- 

 cial Epoch," by J. C. Branner, in the " American Journal of Science," vol. cxxxii, 

 1886, pp. 362-366. 



f "American Journal of Science," vol. cxxv, 1883, p. 339 et seq. 



