486 W. H. HOBBS LINEAMENTS OF ATLANTIC BORDER REGION 



first head of particular significance are the lines of escarpment, the 

 borders of upland areas, and the lines connecting cascades or rapids — 

 fad lines. In so far as surface configuration has been brought about by 

 the influence of fold structures within the underlying rocks, the genetical 

 relationship will be veiled under the complex curves characteristic of 

 such structures, except where the latter are of exceptional simplicity. 

 Any orientation of lineaments due to joints or faults, on the other hand, 

 in so far as this influence is now apparent, will by contrast be indicated 

 in a more or less marked tendency of lineaments to adhere to a fixed 

 direction, and this direction should recur in the orientation of other 

 lineaments within the province. If a system of joints or faults is ex- 

 tended over a broad area, approximate equivalence in the spacing of 

 lineaments may be looked for as a possible additional indication of this 

 origin. In so far as such structures stand near the vertical, as is the 

 case in the post-Newark deformation of the Atlantic border region, the 

 course of such structures should be but very little affected by the irregu- 

 larities of the surface. 



From the existence of several types of lineament, it is to be expected 

 that one which is manifested for a greater or less distance upon the 

 earth's surface as a distinct type — say a scarp — may be continued as 

 another t} 7 pe — let us say as a drainage line — and this -again may be ex- 

 tended by a third — it may be as a "fall line' 1 which intersects lines of 

 drainage, and this again by a geologic boundary, etcetera. This com- 

 posite nature of extended earth lineaments tends to conceal their pres- 

 ence, and careful study will be necessary for their discovery. 



PROJECTION OF LINEAMENTS ON MAPS 



The observation made in smaller areas that the course of a line of 

 dislocation is not straight, but made up of a great number of straight 

 elements composing a series of zigzags, is indication that the lineaments, 

 which may appear rectilinear on the maps, may be so onty in proportion 

 as the scale of the map is small. Such lineaments, if traceable to dislo- 

 cation of the crust for the control of their direction, must be conceived 

 to outline in the majority of instances a complex but comparatively nar- 

 row zone of displacements, in which other directions than that given by 

 the general trend are included. The principal dislocation, while making 

 excursions in zigzags upon either side of its axis, does not, however, it 

 would seem, deviate very far from this average course. Such lines, if in 

 reality the projection of plane surfaces within the crust of the earth, 

 will, upon maps constructed with a polyconic base, appear as curves. 

 This necessary correction in their delineation, like the influence of ero- 

 sion in everywhere molding curving outlines, has often effectively ob- 



