16 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
discussing the phenomena of the more recent formations of the Sierra Ne- 
vada. For further information in regard to the topics of this section the 
reader may consult Geology of California, Vol. L, a considerable portion of 
which is devoted to the Coast Ranges. The material exists for a much more 
elaborate account of the geology of these ranges than has as yet been pub- 
lished, and it is the wish and expectation of the writer that this work shall 
be performed. Meanwhile the brief synopsis which here follows will be of 
service to those who have occasion to use the present volume. 
The most striking fact in regard to the Coast Ranges is, that this very 
extensive group of mountain chains is of comparatively very recent geo- 
logical age. It is made up of Cretaceous and Tertiary strata, with no rocks 
older than these showing themselves in any portion of the complicated series 
of elevations which are properly included under the above designation. 
There are some areas within the Coast Ranges occupied by volcanic rocks, 
and others where granite and granitoid masses make their appearance on 
the surface. But by far the larger portion of these ranges consist exclu- 
sively of sedimentary beds, which have been bent, folded, and crushed, so as 
to form numerous subordinate ranges, as already indicated in the preceding 
section. 
The Coast Ranges resemble the Appalachians in having no central axis or 
dominant range to which the others are subordinated. Neither is there in 
the Californian mountains any core of igneous rock, to the elevation of 
which the folding or disturbance of the sedimentary beds might be attrib- 
uted. There are circumscribed areas where such rocks make their appear- 
ance; but it is evident that these cannot be considered as having played 
any prominent part in the structural development of the system of moun- 
tains in which they occur. The folds of the Pacific Coast Ranges differ also 
from those of the Appalachians in being much less regular and symmetrical 
in their form than are those of the system of mountains which runs parallel 
with the Atlantic side of the Continent. On the western edge of the country 
the work of mountain-building seems to have been much more rapidly ac- 
complished than it was on the eastern. In the first place, the formations 
themselves are far more irregular in development and thickness than are 
those of the Appalachian system; they differ from the latter, moreover, in 
being more or less irregularly broken through by both granitic and volcanic 
outbursts. But the rocks of the Coast Mountains are especially distinguished 
by the fact, that the movements to which they have been subjected, and 
