Whitney's Geology of California. 239 
low on the northwest, and increase in height and breadth to 
near New Almaden, where they attain their greatest breadth, and 
above Mt. Bache, 3780 ft., is the culminating point, then de- 
crease to the southward. ‘These ridges rise directly from the sea, 
without intervening plains along the coast. 
In this series, the Cretaceous strata, so far as seen, are mostly 
altered and very much broken and contorted, and Tertiary rocks, 
mostly of the later groups, are largely developed. The forma- 
tions which compose these ridges on the north are but a continu- 
ation of those found in Marin Co., on the opposite side of the 
Golden Gate and on the south, and they throw out spurs, one of 
which apparently crosses the San José valley by a series of hills 
of highly metamorphic rock a few miles below San José, and 
again by ridges near the southern part, which cross the Pajaro 
Tiver, and connect with the Gavillan range, which series are in 
turn absorbed by the Monte Diablo range farther east. 
Beginning at the north, the most of the rock in and about San 
Francisco is of highly altered Cretaceous, so broken and con- 
torted that no prevailing dip or strike can be observed. These 
Constitute the rocky hills in the city, and about it, and also the 
Most of the rocky islands in the bay. The rocks have precisely 
the lithological character of the rocks of similar age in the Mt, 
Diablo group, and a few fossils have been found to fix the age 
cavil, 
and precisely similar to that in which the same ore occurs at 
) ow Idria, sa Gas and other mines, Monte Diablo, San Pablo 
hills, and the very numerous localities in Lake and Napa coun- 
Imaden, or : 
