Southwestern New England Region. 445 



small attention : first, because the problem of their structure is 

 difficult to solve and perhaps is not regarded as affecting the 

 larger questions of the region ; and, second, because if once 

 solved the scale of the map would not allow of its representa- 

 tion. Such areas are therefore more frequently represented 

 upon the map in the color of the formation which is believed 

 to compose their greater part. 



However unsuited these intricate areas may be supposed to 

 be for establishing the order of succession of geological forma- 

 tions, they are, nevertheless, it is believed, in many cases the 

 keys, and in some cases the only ones, to unlock the secret of 

 the manner of deformation which has affected the region as a 

 whole. Complicated though these problems may be, they 

 often require only patience and industry for their solution, 

 whereas the larger masses by their very simplicity of areal dis- 

 tribution allow of several hypotheses, any one of which would 

 explain them. 



Four areas of exceptionally intricate areal relations and 

 widely separated in the region were selected for study. They 

 are the area of sharp ridges near Lee, Massachusetts ; Evergreen 

 Hill in Stockbridge, Massachusetts ; the Sheffield-Salisbury 

 area; and the Greater New York area. Between the two last 

 mentioned is located the Pomperaug valley area, which, from 

 its detailed mapping, may be counted as a fifth. The Greater 

 New York area has been discussed in papers before the ]STew 

 York Academy of Sciences'* and the Geological Society of 

 America. f 



After working out so far as possible the local conditions of 

 deformation within the circumscribed areas above mentioned, 

 the larger surrounding areas have been studied not only with 

 respect to the kind of rock and the inclination of its plane of 

 lamination at each locality (as usually done), but the broad dis- 

 tribution of outcroppings, the direction of outcrop margins, 

 the lineaments of the landscape as revealed in topographic 

 relief and drainage lines, and the directions of joints and faults, 

 have all been considered in their relation to the structure dis- 

 closed within the smaller areas. 



2. Fault structures are best preserved by the more resistant 

 rock masses. — Revelations of fault structure through the topo- 

 graphic relief are most likely to be made in areas where the 

 more resistant rock masses are at the surface. The perfection 

 of fault structures preserved in the Newark areas is in no small 

 measure accounted for by the presence there of the dense 

 resistant basalt masses. So resistant a type is not found within 



* See review of this paper in Science, xvi, pp. 905-906, 1902. 

 f Head at Washington December, 1902. See review in Science, xvii, 298 

 (1903). 



