2oo POPULAR SCIENCE MONTHLY. 



Fig. 6. Precipitous Cliffs along the Northwestern Side of the Wilmington Notch— 

 illustrating the northeast and southwest type of fault valley. 



depressions were recognizable. The old valleys have gentle slopes and 

 wide expanses. Their contours are softened down and the whole 

 physiographic expression is one which suggests long-continued erosion 

 and maturity of form. In studying out these relations, one has also 

 to eliminate as far as possible the mask of glacial drift which is every- 

 where in evidence. The valleys of the old system run in their most 

 marked development east and west, and north and south. Several 

 of them are occupied to-day by some of the largest streams and lakes — 

 such as Schroon lake, the southern third of Lake George, parts of 

 the Hudson Valley and several tributary to Lake Champlain. One 

 half of an old valley w 7 ill often remain with characteristically gentle 

 slope and mild topography, while the other half of the depression 

 will consist of the steep precipices of the next type. And as the 

 second type has been superimposed upon the first, the observer is often 

 forced to trace the former out despite its disguises and modifications. 



Tbe second type of valley is obviously the result of faulting, and 

 of faulting that is of no great geological antiquity. The sides and steep 

 escarpments and the depressions may have all the characteristics of a 

 ' Graben-senkung,' or of a fjord, if the latter can be imagined away 

 from the sea. In the southeastern portion of the mountains as well 

 as in the interior, three pronounced sets of fault escarpments may be 

 recognized and plotted. The most marked one is northeast, and to 

 it is due the general northeast and southwest trend of the mountains. 

 The topographic maps, and still more the relief model prepared by 



