Lesley.] lyjO [Nov. 4, 



made, it would have the effect of putting a stop to much of that vague 

 babble about the " immense " "enormous" "amazing" influence of the 

 ice age in sculpturing the surface of our planet, which has in some respects 

 demoralized our science. 



Had the age of ice commenced in Laurentian days or even in Permian 

 times and lasted until now, we should certainly be compelled to ascribe 

 most of our topography to the action of ice. But as the ice age was late 

 and comparatively short, we must consider its effect upon our topography 

 not only local but slight. 



The second line of argument, therefore, is a A^ery simple one. We should 

 enquire first, what are the main features, the characteristic elements of 

 our topography ; and secondly, whether those be essentially the same in 

 the glaciated and in the nonglaciated regions. If we find them to be 

 identically the same in both regions, then, it follows, as a matter of course, 

 that they cannot be ascribed to ice. 



This line of argument I have taken numerous occasions, in past years, 

 to follow out, and I have shown that the great lake basins of the north are 

 in all (but one respect) topographically like the great valleys of the south 

 and therefore not excavated by ice. The one item of exception is, that 

 they have been more or less filled with the debris of the ice sheet, and 

 afterwards with water dammed in behind glacial deposits. So far from 

 the glacier having excavated them, it has simply buried them. 



The argument pursued on this grand scale, repeats itself on a small 

 scale now that the Terminal Moraine has been traced across the mountains 

 and valleys of New Jersey and Pennsylvania. If the glacier covered the 

 top of the Kittatinny mountain, for example, along its whole course from 

 the Hudson to the Delaware, and for some miles west of the Delaware, 

 and did not cover it anywhere along its whole course through Pennsyl- 

 vania, Maryland and Virginia (and these facts are now demonstrated) — 

 and if notwithstanding, the mountain in its north-eastern prolongation is 

 precisely the same as in its south-western prolongation — it follows without 

 argument that it existed in its present form before the ice age, and was 

 merely a little sandpapered by the ice during the ice age. 



AVhat is true of the Kittatinny, is true of the (Catskill) Pocono moun- 

 tain plateau behind it, and of the Orwigsburg or Delaware river (Upper 

 Silurian and Devonian) valley which separates the two ranges. Across this 

 broad valley (the analogue of Lake Erie) the Terminal moraine runs west 

 of Stroudsburg. The topography of the valley east of the moraine 

 precisely resembles the topography of the valley west of the moraine, 

 only that it is covered with drift material and marked with scratches. Of 

 course the valley existed before the ice age, and the glacier merely polished 

 its surfaces and protected parts of it from subsequent erosion ; just as the 

 glacier protected lake Erie from erosion, while it scratched the islands of 

 which Prof Newberry speaks, and all the hard outcrops, around it, as 

 described by James Hall in New York, by Carll, White and others in 

 Pennsylvaina, and by Dr. Newberry in Ohio. 



