34 [APPENDIX 



beyond which the primitive rocks again occur, and continue to the ex 

 treme southern point visited. 



THIRD. THE TERTIARIES. These complete the formations found in 

 these mountains. For convenience of description, this class will be 

 sub-divided into the different periods to which they belong. They will 

 occur as follows : 



PERIOD. 

 Eocene. 



Miocene, 



Pliocene. 

 Post Pliocene. 



GROUP. 



Middle. 



Lower. 



WHERE FOUND. 



Calaveras County, at Murphy's, and other local 

 ities. 



Bones of extinct animals, <fec. 



North and south of San Francisco in the Coast 

 and Monte Diablo Mountains. 



Consisting of marine shells with most of the spe 

 cies extinct. 



Coast Mountains and Gabilan Spur. Also in cav 

 ern deposits in Calaveras County. 



Southwest of Monterey. 



Marine shells, all of existing species. 



POSITION AND KELATION OF THE VOLCANIC KOCKS TO 



THE TEETIAEIES. 



Before entering upon a description of the relations of the recent vol 

 canic group with the primitive rocks, it is thought best to examine their 

 positions and effects, among the sedimentary formations, both ancient 

 and modern ; in order to elucidate more distinctly the difference in age, 

 of another group of the volcanic series, which have been described as 

 having been cotemporaneous with those under consideration, and of 

 which there is some question. 



The examination of the Coast Mountains has shown us the fact, that 

 those forces on the west side of the basin, which have been instrumental 

 in elevating the range, have had the effect to produce a series of contin 

 uous and nearly parallel ridges, throughout the greatest portion of their 

 length ; this peculiarity will force itself upon the observation of the 

 traveler if they are crossed at almost any point transversely to their 

 course. 



In many parts of this range, the ridges are narrow, and the decliv 

 ities steep, and the higher isolated peaks are conical. On the summits 

 of these ridges, there are often to be found nothing btit bare vblcanic 

 rocks which are mostly of a trachytic character ; on the sides of some 

 of the hills, which are less abrupt, are to be met beds of sandstones and 

 at times a few slates which from their nature modify and soften the 

 rugged contour of the surrounding country, by their easy disintegra 

 tion from natural causes. 



The. sedimentary rocks, as far as observed in this part of the State, 

 are, without exception, of marine origin the fossils they contain being 



