Geological N~otes on the Sierra Nevada. — Turner. H(i7 
3), similar nodules occur in Bohemia and exclusively in tke hornblende- 
granites. 
Weathering of the Granite. The granite of the Sierra Nevada weath- 
ers in very different ways, producing strikingly different scenic results. 
According to Mr. <;. F. Becker,* the greal granite domes of the Yosemite 
are merely gigantic eases of exfoliation, similar except in scale to those 
observed iii basalt and other rocks. Mr. Becker says: — 
"If the theory of an original controlling ball structure were correct, 
ii would account for the spheroidal weathering of the fragments as well 
as the collosal domes, for between the two exiremes of size there is 
every possible gradation. The laTge domes show no indication of a ten- 
dency to resohe themselves into smaller spheres, excepting when they 
have first been intersected l>\ fissures.") The surface waters acting 
along these fissures would produce decomposition, the exposed corners 
would scale off, and as a result moi r less nearly spheroidal bodies 
would finally result . 
Considerable portions of the sierra Nevada an' intersected by systems 
of fissures more or less nearly parallel. According to Becker,! this is a 
result of pressure from forces acting in definite directions. As a con- 
sequence of this, the granite in places possesses a laminated structure 
which is perhaps nowhere better shown than in Alpine county to the 
northwest of Charity valley. There are here a set of Vertical north and 
south fissures and another set nearly horizontal. Erosion of the granite 
produces vertical walls along the vertical fissures and terraces along the 
horizontal system. 
That portion of the crest of the range between Tower peak and 
Mount Conness is chiefly composed of granite-porphyry, which is inter- 
sected by very abundant fissures so thai the rock is divided into small 
polyhedrons of varying shape. Asa result the crest hpreassumesa verj 
serrated ou1 line. 
Analyses of Granites.*; 
Biotite-hora- (iranite-por- 
Granodiorite. blendn granite, phyry- 
No. H4r». No 19, No. 2.".. 
Plumas County. MariposaCo. Mariposa Co. 
Silica : 50.83 72.48 66.28 
Alumina 14.06 16.03 
Lime 6.40 ■!.]; 3.75 
Magnesia .62 1.12 
Potassa 1.60 1.75 3.40 
Soda 3.53 3.30 1.1" 
*Tenth Ann. Rep. IT. S. Geol. Survey, p. 142. 
|Mr. Becker discusses the subject more fully in Monograph xin, U. S. 
< ieol. Survey, p. 68. 
fBull. Geol. Soc. Am., vol. n. pp. l0-*3 1. 
gNearly all of the analyses contained in this paper were made i>\ Dr. 
W. F. Hillebrand of the U. S. Geol. Survey , 
