TWO' MOUNTAIN EANGES OF SOUTHERN CALIFORNIA 661 



The similarities, liowever, disappeai- wlien the land forms are examined. 

 The San Gabriel range has been completely dissected, resulting in tui^rougaiy 

 graded streams, sharp peaks, and knife-like ridges of discordant heights. x\o 

 level areas at or near the summits, nor in the valley bottoms, exist within the 

 mountain mass. The San Bernardino range contrasts sharply with its neigh- 

 bor in these respects. Throughout its western end there is a strikingly level 

 sky-line at an elevation of 5,000 feet or more. It contains many broad 

 meadows, with lakes and playas, separated by smooth ridges. The topography 

 of the central part is, in brief, topography of an old, well reduced type. About 

 its periphery, however, topographic forms are strikingly new. Several of the 

 streams are not reduced to grade ; they meander through broad uplands in the 

 central part of the range, then plunge over falls into steep canyons, which 

 they follow to the valleys that border the ranges. 



For these striking topographic differences there seems to be no adequate 

 explanation in the rock types, in the relative masses of the ranges, in their 

 relation to major drainage lines, nor in their relation to precipitation. It is 

 concluded, therefore, that since each is a faulted, uplifted block, the San Ber- 

 nardino mass, in which old topographic forms are well preserved, is much later 

 in origin than its neighbor, the San Gabriel range, in which none of these old 

 forms are now to be found. 



The Section then adjourned for the day. 



Session- op the Cokdilleean Section, Saturday, December 29, 1906 



The meeting was called to order at 9.15 a m b}' the Cliairman, and 

 proceeded immediatel}' to the reading and discussion of papers presented, 

 as follows : 



RELATION' OF THE LOS ANGELES-OWENS RIVER AQUEDUCT TO THE FAULT 

 LINES OF INYO AND SAN BERNARDINO COUNTIES 



BY J. 0. BRANNER 



NOTES ON THE GEOLOGY OF THE MOUNT HAMILTON QUADRANGLE 

 BY JOHN F. NEWSOM AND RODEEIC CRANDALL 



[Abstract] 



Discussion of the geological terranes present, their distribution and rela- 

 tions; of the main structural features, with special note of the latger faults 

 and direction of movement ; and of the relations of structural features to the 

 topography. 



CRETACEOUS STRATIGRAPHY OF THE SANTA CLARA VALLEY REGION 



BY RODERIC CRANDALL* 



[Abstract] 



The fossils from the Cretaceous localities are listed accoi-ding to their geo- 

 graphic distribution. Probabilities of the presence of Horsetown at mount 



* Introduced by J. F. Newsom. 



