56 



W. R. BROWNE. 



Taylor's map (Fig. 6 in Bulletin No. 6, referred to above) 

 reveals a very suspicious parallelism in the courses of many 

 of the tributary streams, such as commonly and almost 

 inevitably results from the presence of directive structures, 

 as for example, schistosity or gneissic foliation, or more 

 probably in this case, shear zones, fault planes or joint 

 systems. 



It can be seen that this same principle applies also, where 

 beds of varying degrees of hardness have been folded or 

 tilted. If, for example, a stream flows obliquely across an 

 anticline, some of the component beds of which are softer 

 than others, the tributaries which develop as subsequent 

 streams will, as erosion proceeds, tend to carve out valleys 

 along the junction of the hard and soft beds, and it is 

 evident that the direction of these tributaries will be 

 normal on one side of the main stream and abnormal on 

 the other (Fig. 1). Pursuing the investigation a bit farther, 



Fig. 



one can see that if the anticline in question has a pitch, 

 the tributaries flowing along its flanks may diverge, giving 

 all the features of a breached divide. (Fig. 2). 



