82 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
than now when it was first upfaulted, and that it has lost its initial 
height and steepness in the same time and by the same processes that 
have sufficed for the dissection of the slide. On the other hand, if 
the Canyon range is regarded as a mere residual of a once far-and- 
wide stretching mountain mass, instead of as a maturely dissected 
fault block, the occurrence of such a landslide is altogether incom- 
patible with the very advanced stage of erosion that must be as- 
Fra. 11.— East-west section through the Canyon range along the valley of Oak 
creek: length about eight miles. 
signed to the range when the slide occurred. The desert plain, at 
least 30 miles wide to the westward, might, as far as general geo- 
logical possibilities are concerned, be the result of wide-spread pene- 
plaination; but if that were the origin of the plain, the range at its 
border would have been reduced to slopes of so gentle a declivity that 
the occurrence of a large landslide on its decrepit flanks would be 
impossible. 
Sections of the Canyon Range. The following day we made an | 
EAS 
Fie. 12.— East-west section of the Canyon range along the valley of Dry creek, 
about two miles south of Oak creek: length, about eight miles, 
excursion up the valley of Oak creek eastward to its head in the crest 
of the Canyon range, which here lies close to its eastern side. There 
we turned south along the slope of its eastern face, with the desert 
plain far below, and then returned to Oak City by the valley of Dry 
creek. The range is thoroughly dissected and its slopes are very gen- 
erally graded. We saw no forms that could be safely referred to an 
