426 
Frank Carney 
least approximately so, and should likewise show the effects of 
rather speedy giving away to certain stresses. This type of fold 
probably is represented in the Moravia quadrangle, one example 
at least having been noted. But the folds in question cannot be 
explained as due to buckling. 
Campbelk^ has described folds which result from normal 
weathering of superficial formations. The weathering being 
localized along joints, there results, particularly when these joints 
are numerous, a very appreciable lateral extension which at some 
point in the horizon overcomes the normal pressure and produces 
a fold. Both the mode of production and the type of fold pro- 
duced, which in all cases illustrated are symmetrical, preclude 
this explanation for the folds in question. 
The only remaining explanation seems to be that of over-riding 
ice. We have little data of exact observation detailing the method 
of ice-erosion. When the country being transgressed bears a 
mantle of residual soil, this is removed before the less weathered 
horizons become subject to ice abrasion. Considering the great 
weight of over-riding ice, we apprehend that friction between its 
base and the underlying surfaces accounts for the removal of great 
areas of partially weathered rock. The distorted horizons above 
figured seem in harmony with such a method of removal. This 
being the case, then, these folded horizons indicate a zone where 
ice-erosion has been less efficient. 
Fig. 25 shows that the direction of ice-motion was more 
nearly north-south. Fig. 26, in which the fold is turned east- 
ward, implies a flow of ice in that direction. The former locality, 
is quite in line with the direction of ice-motion for this region. 
The latter locality suggests rather a movement of the declining 
Owasco lobe, when on the eastern side it fed outward from the 
main axis of the valley. This outward movement of the ice in 
valley lobes has long been known. These figures therefore illus- 
trate both linear and lateral motions of the Moravia lobe. 
The areas shown have been selected from several photographs; 
some of them, however, represent less distortion. 
As already suggested, theoretical considerations point to greater 
activity of ice as an eroding agent in the lower contours of these 
longitudinal valleys. On the west side of the valley south of 
M. R. Campbell: Jour, of GeoL, vol. xiv (1906), pp. 226-32. 
