386 Prof. Blake on the Diluvial Deposiis in California. 
morphic rocks: the former are mostly porphyritic in the lower 
hills, whilst higher up trachytic rocks are more frequently met 
with: The metamorphic rocks consist of micaceous schists, 
slates both talcose and micaceous, metamorphic sandstones, and 
limestones, with occasional beds of conglomerate. The stratified 
rocks have all been much displaced; it is rare to-find them with 
a dip of less than 7U°, and they are generally very nearly per- 
pendicular. The strike of the beds in that section to which my 
mensurate or nearly so, with that of the gold bearing region, in 
that part of the country. which I have examined. They are 
the country, but besides being found on the crests of the ridges, 
where their extent frequently does not exceed a few yards in 
breadth, they are also met with covering in the extensive eleva- 
benches between the different water 
courses, forming continuous beds of some miles in extent, which 
are rarely interrupted by the protrusion of any of the older rocks. 
Where found in these elevated situations, the lower hills and val- 
leys are entirely free from them; frequently a large section of 
country will be enclosed between two high ridges capped by de- 
posits and diverging from a common point; in the intervening 
space seen many secondary ridges, sometimes. aD 
