MERGING OF NETWORK PATTERNS 



141 



sharply rectangular pattern having subequal space intervals is in contrast 

 with a more intricate pattern to the east of the npper Sorf jord (see figure 

 17) . Such a merging of patterns is schematically represented in figure 18. 



PATTERNS OBSCURED BY BEDPLANES AND FORMATION BOUNDARIES 



It needs to be emphasized that the evidence of control of relief by frac- 

 tures on the one hand or by folds on the other, will in general be ex- 

 pressed by the straightness or the curvature respectively of the stronger 

 lines in the plan. This is well illustrated by a comparison of figures 

 1 and 2 (see pages 125 and 126). In the case of folds, it appears to be 



Figure 18. — Schematic Representation of the merging of two Relief Patterns 



the strength or weakness of rock beds which are the determining factors, 

 and a similar curvature but generally lesser regularity of lines will result 

 from the presence of intrusive igneous rocks in other forms than dikes, 

 which latter, being located upon fractures, exert their influence upon the 

 relief in a similar manner. In proportion, then, as fold structures are 

 prominent and fracture systems but little developed in any given dis- 

 trict, repeating patterns will be obscure and often indistinguishable by 

 the eye alone. Thus the effect of folding is added to that of erosion in 



