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University of California. 



[Vol. 3. 



clearly formulated to bring about their speedy rejection. It 

 might be supposed, for instance, that they represent resid- 

 uals of erosion in the down cutting of the canon, but this 

 is negatived by the fact that, in the intervals between the kern- 

 buts, the canon floor has its normal width, and by the fact that 

 there is no evidence of the kerncols having ever been stream 

 channels except in one case, where the kerneol is a little above 

 the present level of the river. It fails, however, to explain the 

 prevailing landslide profile which these kernbuts habitually 

 affect. But even when we accept, as our working hypothesis, 

 the statement that the kernbuts are masses which have been 

 detached from the west wall of the canon, much remains to be 

 explained concerning them. They may, for example, be inter- 

 preted either as of the nature of landslides, or as the butt end of 

 wedges, which have dropped into a rift or chasm opened in the 

 earth's crust along the line of the canon. The former hypothesis 

 is the less violent of the two, and may be examined first. 



Landslide Hypothesis. — In such an examination one turns 

 naturally to a method of comparison with features due to land- 

 slide action. Now it must be confessed, to start with, that the 

 geomorphic configuration of these kernbuts is somewhat analo- 

 gous to that produced by landsliding. In ordinary landslides 

 large or small, the mass which slips is usually of a more or less 

 plastic material, and suffers a partial rotation on an axis paral- 

 lel to the slip surface. It suffers both plastic deformation and 

 dislocation, and, when it comes to rest, it presents a profile 

 which is characterized by a series of steps. The tread of these 

 steps is in all cases a slope of less inclination than that of the 

 original hill or mountain side in consequence of the rotation 

 above referred to. In many cases this rotation has been so great 

 that the tread slopes down towards the hill-side, giving rise 

 perhaps to a basin. The rise in the step is in all cases a disloca- 

 tion plane in the slipped mass, and usually hades outward or 

 away from the hill side. In these cases, where the rotation is 

 extreme, the profile of the slipped mass is analogous of that pre- 

 sented by the kernbuts. On the basis of analogy with ordinary 

 landslides in plastic material the kernbuts might be supposed to 

 have a similar origin. 



