Whitney's Geology of California. | 235 
: formations forming the plains. If the Eocene exists here or 
‘ ! tere in the state, its presence has not yet been proved by 
: Ossils, 
J Lying west of this mass is a lower range of ridges known as 
: the San Pablo hills, which are eight to twelve miles wide; they 
3 continue distinct from the main chain for over fifty miles, and 
then unite with the Mt. Hamilton group. Opposite San Fran- 
cisco they are 1400 to 1700 ft. high, but farther north they rise 
to near 2000 ft. Between this and the main chain are two val- 
leys, like basins; the drainage of one is north to the straits of 
Carquines; the other is drained through a break in the hills 
Some future time, furnish the available gap 
ivermore Pass being 
ing the highest point within sight of San Francisco, Mt, Hamil- 
On, 444 ft Hees the chain is wider and very rough, denuded 
etamorphic _ 
belt of unaltered Cretaceous, in plat Kas ais ON ipay £ 
‘Ress. At Arroyo del Puerto it is believed to be over 20,000 ft., 
_ the whole dipping. to the east, and consisting of heavy beds of 
Sandstone, with interstratified shales, and some ee oe 
aces of most enormons thick- : : - : 
