Lawson.] 



The Upper Kern Basin . 



367 



the cirque cliffs, while in other cirques little or no talus exists. 

 The bevelled edges of the upper part of the cirque walls are in 

 several cases curiously fluted. This fluting is well seen in Plate 

 42. It appears to represent a post-glacial process of degradation 

 due to small snow-slides following the same paths year after 

 year. This process of erosion may in many cases be correlated 

 with the talus accumulations at the base of the cliffs. There has 

 been no appreciable rock disintegration of the glaciated surfaces. 

 Even where the floors and walls of the cirques and canons 

 have been exposed continuously to the weather, with no other 

 protection than the snows of winter, the glacial polish, striation 

 and fluting are perfectly preserved. They appear to have 

 resisted the weather many times more effectively than equally 

 unprotected surfaces in the region of the great lakes, and their 

 exposure to the weather is, therefore, inferred to have been many 

 times less prolonged. The stream erosion is best exemplified in 

 the trench, perhaps on an average 20 feet deep, which has been 

 cut in the glaciated floor of the upper part of Kern Canon, but 

 probably the greater part of this was cut while the ice still occu- 

 pied the cirques in the rim of the basin. 



The writer has ventured to make a guess at the time ratios of 

 the divisions of the Quaternary which are indicated in the 

 various stages of the geomorphogeny of the Upper Kern Basin. 

 It appears probable that it required eight times as long a period 

 for the evolution of the High Valleys as for the down cutting of 

 Kern Canon. The cutting of Kern Canon probably required 

 six times as long a period as was necessary for the glacial 

 sculpture of the High Mountain Zone. And the glacial sculp- 

 ture fifty times as long as the period that has elapsed since 

 the disappearance of the glaciers. If, therefore, we take post- 

 glacial time as 1, the ratios would be as follows: 



I Evolution of High Valleys 2400 



II Period of canon cutting 300 



III Glacial period 50 



IV Since disappearance of the glaciers 1 



The figures have not much value, the data for a proper esti- 

 mate of these ratios being entirely inadequate . But they at least 

 bring the relation of the period of glaciation to the entire period 



