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The Berkeley Hills. 



35 1 



The Basalts 



Constituent Minerals. 



Varieties 



Chemical Characters 



427 

 427 

 43i 

 433 

 •434 

 435 

 ■437 

 •437 

 .441 



The Pyroclastic Rocks 



Rhyolitic Tuffs and Agglomerates 

 Basic Tuffs 



The Sequence of Lavas, 

 Historical Summary 



INTRODUCTION. 



The Berkeley Hills have rather vague limits. The term is a 

 popular one applied with a certain affection to the range which 

 overlooks the city of Berkeley and the Bay of San Francisco. Its 

 culminating point rises, a little to the east of the University of 

 California, to an altitude of nearly 2,000 feet above sea-level. From 

 Berkeley the range extends southeastward, behind the city of 

 Oakland, with a very even and continuous westward front, off 

 towards Mount Hamilton, into which it merges. To the north- 

 west it persists as a prominent feature of the landscape to the 

 mouth of San Pablo Creek, beyond which it continues only in the 

 form of rolling hills of comparatively low elevation. On the east 

 this range is delimited by San Pablo and Moraga Valleys. It is 

 thus but a simple ridge, though a dominant one, of the belt of the 

 Coast Ranges, which is generally known as the Mount Hamilton 

 Range, and which includes many separately-named ranges and 

 groups of hills. 



To what portion of this range the term Berkeley Hills applies 

 is rather a matter of popular usage than of scientific determination. 

 Whatever may be their extent, the heart of the Berkeley Hills is 

 the field discussed in the present paper. The study is by no means 

 exhaustive, and the area considered is practically limited to that 

 represented on the accompanying map, except for occasional drafts 

 on information obtained from adjoining portions of the Coast 

 Ranges to supplement the observations here recorded. 



The area embraced in the map is less than six square miles, and 

 represents only about one-fifteenth of the cross section of the Coast 



