Vol. 4| Law son. —Features of the Middle Kern. 407 



were the case, then it is difficult, as before, to see why it should 

 not have determined the main line of canon corrasion instead of 

 the one now followed by the stream. If the supposed structural 

 line, a rift for example, had come into play after the main canon 

 trench had been deeply incised, results might ensue by subse- 

 quent corrasion which would be consistent with the facts 

 observed. We have in this set of assumptions, therefore, a pos- 

 sible explanation of the phenomena. It is, however, less prob- 

 able than another hypothesis discussed below. 



Another hypothesis which the writer attempted to apply was 

 suggested by the resemblance of these features to the kernbuts 

 of the Upper Kern and the possibility of their having the same 

 origin was considered. The analogy of these features with the 

 kernbuts breaks down, however, under examination. In the 

 Upper Kern Canon the kernbuts cause constrictions in the canon 

 and in the interval between them the canon bottom has its full 

 width. In the case of the ridges and buttes of the Middle Kern, 

 the width of the lower portion of the canon is not affected by 

 their presence. The intervals between the buttes and ridges are 

 purely erosional products and the prominences which are thus 

 separated cannot be regarded as portions of a long narrow fault 

 block which have failed to sink as far as the intervening portions. 



There are two other hypotheses which must be examined as 

 possible explanations of the phenomena under consideration. 

 Both of these involve faulting and they differ essentially in the 

 position of the fault, its hade, and the direction of the down- 

 throw. The first of these supposes that the long but now dis- 

 sected defile was originally the trench of the Kern, and that 

 when in the course of its downward corrasion it had reached this 

 depth, a fault occurred on the west side of the canon with a 

 downthrow to the west. In this way a trough might be formed 

 deeper than the trench of the Kern and into this the drainage 

 would naturally flow leaving the old channel stranded above the 

 brink of the new diastrophic canon. The erosional modification 

 of this stranded channel and of the ridge between it and the new 

 channel might give us the feature we are seeking to explain. 



The second hypothesis states that after the canon of the 

 Middle Kern was well advanced, a fault occurred within the 



