WIDE AREA OF REGIONAL JOINTS 503 



(1) The ' passes,' . . . and many other narrow gorges with precipitous 

 sides, evidently produced by fault scarps with a talus. Often a stream forms a 

 waterfall in an especially narrow gorge, and the crushed and strained rocks are 

 shown in excellent exposure. . . . 



" (2) Many ridges have a comparatively abrupt face on one side and an even 

 ascent on the other. Split Rock ridge in Westport and Essex is a good illustra- 

 tion. ... If one climbs any of the hills in central Moriah and looks west- 

 ward the horizon line of the mountains is a saw-toothed profile with a low ascent 

 and a steep drop, many times repeated. . . . 



"In many cases these faults afforded a start for lines of drainage which have 

 now worn out the valleys to broad reaches and have masked their origin. The 

 old scarps at present are rounded and worn down." 



An area within the region described above by Kemp, and one where 

 the lineaments are in correspondence with the controlling lineaments in- 

 dicated on the map of plate 45 for the area of the central states, is shown 

 in plate 47. 



As a result of his extended study of joints throughout the state of 

 Wisconsin, Buckley has made the following summary : * 



"As will be seen in the accompanying map, the joints of the sedimentary rocks 

 strike in four main directions. The prevailing general direction of the joints is 

 N. E. and S. W. The other directions are N. W. and S. E., E. and W., and N. 

 andS." 



Insufficient as is the evidence for a satisfactory correlation of joints 

 and faults within the area studied, it is at least accordant and strongly 

 favors the view that master joints and master faults as well are not 

 without relations to one another, even though separated by distances 

 which may constitute an appreciable portion of the earth's circum- 

 ference. The nearly meridional direction of jointing was found to be 

 dominant in all the areas studied from Massachusetts to Wisconsin. 

 The nearly equatorial and the two bisecting directions were the remain- 

 ing directions of master joints in all save one of the districts examined — 

 the Boston basin — and here the meridional and equatorial directions 

 alone controlled. Observations by the writer in southwestern Wisconsin 

 reveal there the same four directions of master joints. It is to be hoped 

 that other investigators will give attention to the orientation of joint 

 planes in connection with their study of local districts and put the results 

 of their study on record. 



Relation of Lineaments to the grander Features of the Earth 



It must be evident that if the master lineaments within a large area 

 reveal a control by disjunctive processes of the same type and referable 



*Loc. cit., p. 459. 



