SOME INSTANCES OF MODERATE GLACIAL EROSION 161 



the surface. That this clay is not the result of postglacial decay is 

 proved by the fact that in some places the stria? on the sandstone 

 caps are not yet destroyed by weathering. 



It is only occasionally that cuts fresh enough to reveal the actual 

 condition are found, but it is evident in the field that unremoved 

 products of rock decay are widespread. This is proved by the 



Fig. i.— Decayed shale between sandstone layers, one mile east of Berkshire, 

 N. Y., on Harford (U. S. Geological Survey) Topographic Sheet. The shale shows 

 spheroidal weathering and between the nodules is residual clay. 



presence in the fields of abundant slabs of sandstone, many of which 

 are profoundly decayed, with a deep rim of oxidized rock, and with 

 fossils completely weathered out. Very often plowing has encountered 

 weathered sandstone caps under the thin upland soil, and, by upturn- 

 ing the slabs, has transformed the fields to such stony areas that the 

 sandstone fragments cover fully 50 per cent, of the area. The till 

 of this region is made up largely of local sandstone fragments, mixed 

 with residually decayed clay and a relatively small proportion of 

 foreign stones and rock flour, making a very peculiar soil. The 



