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University of California. 



[Vol. i. 



differences in their resistance to erosion, the effect of such a process 

 of sculpture would be an orderly alignment of the resultant peaks 

 and ridges. But this condition obtains only to a limited extent in 

 the Wild-cat Series. Differences in the hardness of the beds are 

 .light, and it was apparently often some trivial accident that deter- 

 mined which of several soft beds abutting upon the transverse canon 

 was to be the line of subsequent drainage at that place. The same 

 beds were not followed in the different transverse ridges nor always 

 on opposite sides of the same ridge. Thus a disorderly arrange- 

 ment of the resultant peaks and ridges has arisen. 



From what has been said it will be apparent that the topography 

 of the Wild-cat terrane differs essentially from that of the other ter- 

 ranes of the coast to the southward in the greater amount of degra- 

 dation that has been effected. The sculpture has proceeded more 

 rapidly and along more numerous lines of action. This fact would 

 be expressed according to the method adopted by Davis, who has 

 done so much to advance our knowledge of geomorphic evolution, 

 by stating that the topography is older or more advanced than that 

 where the sculpture has been less effective. Such a statement is 

 true and is very graphic and useful; but it is not the whole truth, 

 and is apt, therefore, to be somewhat misleading to those not fully 

 cognizant of the facts of the case. It suggests the idea that the 

 other more resistant terranes will in their evolution pass through a 

 condition similar to that now presented by the Wild-cat terrane. 

 This is not the case. The terrane of hard Mesozoic sandstones of 

 the coast will never at any stage of its degradation yield a topog- 

 raphy resembling the present topography of the Wild-cat terrane. 

 When the former has reached the stage in the geomorphic cycle 

 analogous to that which the latter has now attained, it will have a 

 very different character. The difference in character will be radical, 

 and will be due to geological conditions inherent in the construc- 

 tional or block form. The variability of these conditions, moreover, 

 is not only accountable for radical differences in topographic char- 

 acter at the same stage of the cycle, but also gives rise to different 

 stages of degradation in the same block under the same erosive 

 forces, acting for the same length of time. This latter point is 

 important when topograph}' is used as evidence in problems of 



