Studying the Yosemite Problem 



147 



work, still retains very largely the features given it by normal 

 weather-and-stream erosion prior to the advent of the ice. 



But one other line of studies will here be mentioned, namely 

 that of the evolution of the remarkable cliffs and domes of 

 the Yosemite landscape. That the domes have acquired their 

 rounded forms through the progressive casting off of shells 

 — through exfoliation, as it is termed, — has long since been 

 recognized. That a similar process may be at work on the 

 faces of many of the great mural cliffs has been surmised 

 before and at least tentatively announced. It seemed desir- 

 able to verify the correctness of that interpretation, and ac- 

 cordingly many observations were made on the cliffs and the 

 materials composing them. In the main it was found that ex- 

 foliation is rather more general in the Yosemite region than 

 has commonly been supposed, and that many of the slabs 

 and sheets clinging to cliff faces are really products of ex- 

 foliation, that is, of external influences, instead of being rem- 

 nants of structures originally existing in the granite. It 

 would appear therefore that in the Yosemite region massive 

 rock prevails to a far greater degree than at first sight seems 

 to be the case. And this fact must necessarily influence our 

 views as to the amount of excavating to be accredited to the 

 ice : in materials so unfavorable as massive granite it seems 

 unlikely that glaciers would have been able to accomplish any 

 great results. 



In conclusion it should be said that last summer's investiga- 

 tions, elaborate though they were, are not to be considered 

 exhaustive nor at all complete. Some portions of the Yo- 

 semite district were accorded but little more than a cursory 

 glance and will require more thorough study. Again, it 

 seems important that the principal conclusions reached be 

 tested in other parts of the Sierra Nevada, and that the evo- 

 lution of the Yosemite Valley be compared with that of each 

 of the other Yosemites. It is sincerely hoped that this may 

 be accomplished during the present year. 



