ICE-SHEET EROSION IN NEW YORK 51 



facts nor opinions favoring deep localized erosion. Professor H. P. 

 Cushing writes: 



"My impression is that the northern slopes of the region have been consider- 

 ably smoothed by ice action in its uphill climb there. There are cirques in the 

 high peak district, and possibly a number of rock-basin lakes. Some of the passes 

 may have been shaped by ice action. The rocks are very hard, but they are also 

 much jointed, so that plucking might well go on along valley sides. There has 

 been a tremendous amount of rock material, much of it very fresh, moved about 

 by the ice, but it is of course impossible to say whether any amount of it was 

 actually quarried by the ice or not. The joints would facilitate it if such action 

 does take place. Certainly all rock in any way weathered was removed by the 

 ice. The whole surface is rochemoutonneed, especially on the north, where 

 nearly all rocks are absolutely fresh. Even the diabase dikes, which are of pre- 

 Cambrian age, often show the olivines perfectly fresh, and this when they cut 

 hard, resistant granitic gneisses, which are worn down to the same plane as the 

 dikes. I am sure there is no evidence in northern New York that the ice has cut 

 any valleys." 



Professor G. H. Smj^th, Jr., gives testimony to the same effect. 



The most definite observation directed to this subject has been placed 

 on record by Doctor Gilbert* and it is negative. This is the more sig- 

 nificant, since it occurs in writing which favors the conception of ice 

 erosion. After referring to the paper by Goodchild (see page 33) and 

 expressing the opinion that the district of the Finger lakes " owes more 

 to ice work than to antecedent water work," he writes as follows : 



" . . . , and in northern New York, where the rocks are comparable in 

 hardness with those of the Scottish district, the ice seems to have accomplished 

 comparatively little. Sandstones and limestones are not there so disposed as to 

 afford good comparative data ; but in a tract of crystalline schists lying northeast 

 of Carthage and nearly bare of drift, the sculpture features are very different from 

 those depicted by Goodchild. The principal structure of the schist is vertical, and 

 its trend makes wide angles with the direction of ice motion. The ridges, which 

 are at most only a few score feet in height, conform in trend with the strike of the 

 foliation, and have been but slightly remodeled by sculpture on lines of ice motion. 

 The bosses of the moutonnee pattern are measured by yards or rods." 



The locality near Carthage, lying on the northwest flank of the Adi- 

 rondack massif, should have experienced vigorous erosion, since the ice 

 crowded past and around the highland mass. 



WORK OF THE ONTARIAN LOBE; WESTERN NEW YORK 



On the Niagara escarpment. — Fortunately for our study we have in the 

 Niagara escarpment, which extends east and west, parallel to the south 

 shore of lake Ontario (see figure 2), a broad feature of preglacial topogra- 



*G. K. Gilbert: "Glacial sculpture in western New York." Bull. Geol. Soc. Am., vol. 10, 1899, 

 pp. 121-130. 



