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GEOLOGY OF THE SIERRA NEVADA. 39 
able number of thin shells lapped over each other, like the coats of an 
onion.* 
This structural arrangement of the granitic masses exhibits itself in a 
great variety of forms, according as more or less of the original dome has 
disappeared, either from actual engulfment or from the action of erosive 
forces. The “dome-structure” of the granite, as it has been called in Geol. 
I., is by no means peculiar to the Californian mountains; on the contrary, 
it is most conspicuously displayed in many other parts of the world, although 
perhaps nowhere on so grand a scale as in the Sierra Nevada. It was first 
noticed and described by Von Buch as occurring in the Harz, in the Scandi- 
navian Range, and in many other regions.t The same phenomena have also 
been described and figured by Helmersen.t 
No one who has studied the Sierra Nevada with any care can doubt the 
eruptive origin of the granitic nucleus or axis of that chain. The remark- 
ably homogeneous character of the rock over such a vast area adds weight 
to the evidence of an intrusive origin of the granite furnished by its position 
in reference to the sedimentary strata with which it is connected. The inti- 
mate connection of the volcanic deposits of the Sierra with the granite must 
also be considered in reference to this question, as will be noticed farther on. 
The epoch of the granitic outburst may best be indicated after having made 
some acquaintance with the geology of the stratified deposits through which 
it has made its way to the surface. 
Of the lithological character of the auriferous slate series — the bed-rock of 
the miners, as already explained — we shall have frequent occasion to speak 
in the detailed descriptions of the overlying formations, to be given in the 
next chapter. A few general remarks in regard to the nature of the rocks 
of which this series is made up may, however, be introduced at this point, 
and it will be desirable first to give a brief synopsis of what is known in 
regard to their geological age. 
The geological age of the auriferous rocks, of the Sierra Nevada had 
remained, up to the time of the beginning of the work of the Californian 
* This is well seen in the photograph of Mount Hoffmann, in the “ Yosemite Book,” also in several of 
Watkins’s series of photographs of the Yosemite and its surroundings. See also Geol. I., for a number 
of sections and cuts illustrative of this structural arrangement of the granitic masses of the Southern 
High Sierra. 
+ See Abhandlungen der Akademie der Wissenschaften zu Berlin. 1842. pp. 57. 
t Memoirs of the St. Petersburg Academy. Vol. XIV. No. 7, 1869. Studien iiber die Wanderblicke 
und die Diluvialgebilde Russlands. 
