Lawson. 



Post-Pliocene Diastrophism. 



Besides these great terraces, which contour the southwest side 

 of the island up to an altitude of 1,320 feet, there are observable in 

 other parts of the island, particularly along the gentle longitudinal 

 slope from Wilson's Cove to the summit, many less prominent ter- 

 races occupying the same vertical interval. On this trail there were 

 observed no less than eighteen distinct terraces, two of them exceed- 

 ing in elevation the 1,320-foot ten ace. The altitudes of the ter- 

 races at the rear are given in the following table: — 



Aiuiuucb 01 terraces, as uctci- 



mined by aneroid on trail from 

 Wilson's Cove to the summit. 



Altitudes of terraces on S. W. 

 side of island, as read from Coast 

 Survey MS. map, to the nearest 

 40-ft. contour. 



1,500 feet. 





r >375 " 







T "> Id ff^pr 



1,250 " 



I ,240 " 



1,040 " 



I ,040 " 



960 " 



96O " 



930 " 





785 « 



8OO " 





68O " 



580 " 





550 " 



560 " 



470 " 



480 " 





44O " 



380 " 



400 " 



325 " 



320 " 





280 " 



225 " 



200 " 



170 " 



l60 " 



120 " 



120 " 



85 " 



80 " 



40 " 



40 " 



12 " 





given at second-hand is the most valuable and authentic information on record 

 of perhaps'the most important geological event on the coast of California since 

 the post-Miocene uplift. Dr. Cooper's observations have met with but scant 

 courtesy from geologists, and the correctness of his interpretations has been 

 doubted ever since the appearance of Mr. Davidson's paper, above referred to, 

 in which the origin of the terraces was ascribed to ice action. The present 

 writer verifies Dr. Cooper's observations and conclusions and extends them. 

 2 



