328 BULLETIN OF THE 



eras, and this as we know elsewhere shows a tendency to valley form. 

 We had not time to study the origin of the basin of Green Lake, the 

 largest of the district. 



The large blocks of Corniferous limestone, weathered loose along its 

 margins, may be mentioned again here. The best examples are on the 

 Old King's road where it joins. the Mountain road; several of the 

 blocks are eight or ten feet cube. They cannot be considered simply as 

 glacial boulders, for they occur only along the disappearing margins of 

 their formation ; they cannot be of pre-glacial weathering, for the ice 

 stream that filled the Hudson valley till it overflowed its mountain 

 bomidaries east and west can hardly have left any loose blocks so near 

 where it found them. So we are forced to consider them largely the 

 product of post-glacial weathering, mostly by solution ; but this gives a 

 so much greater measure of post-glacial erosion than is generally found, 

 tliat it is not satisfactory. Some of the blocks are separated from one 

 another and from the still continuous bed out of which they seem "to 

 have weathered, by a hundred feet or more. The limestone would 

 therefore have to be easily dissolved by surface waters, although it is 

 very dense physically ; and yet the same limestone under the clays of 

 the Marcellus valley, where much water must have filtered in along the 

 contact of rock and clay, has not lost its glacial scratches. The case is 

 not satisfactorily explained. 



All the lower valleys are occupied by stratified clays capped with 

 sands up to about one hundred and fifty feet above the Hudson (tide- 

 water). Near the river, the area and often the depth of these clays are 

 very great ; they cover all but the higher sandstone ridges, which crop 

 out as rocky islands. Farther back from the river, the clays fill the 

 depressions among the limestones, as is nicely shown in the Fuyk, when 

 viewed from the Lower Pentamerus cliff on the east ; and the long 

 valley cut on the Marcellus shale, where it is followed by the Kaaters- 

 kill and far north and south as well, is deeply buried under the clay 

 terraces. 



It is easy to see that, if the clays were stripped off, and the country 

 elevated several hundred feet as it has been in the past, its valleys and 

 drainage would be considerably changed from their present arrangement ; 

 but just what these changes would be is difficult to say. I think it 

 probable, however, that the Kaaterskill would leave the Hamilton a 

 little to one side of its present course at Big Falls ; that both the Kaa- 

 terskill and the Catskill would run along the Marcellus valley at a 

 lower level than their present beds, and would escape eastward by some 



