28 APPENDIX 



of the great basin separating the Coast Mountains from the Sierras will 

 be given ; and in speaking of the Sacramento Valley, that of the San 

 Joaquin will also be included, and the physical characters of both brief 

 ly explained. 



STKUCTUKE OF THE VALLEYS OF SACKAMENTO AND 



SAN JOAQUIN. 



These valleys forma "single geographical formation,"* stretching 

 from the terminal spurs of the Cascade Mountains at the north, to the 

 junction of the Sierra Nevada with the southern terminus of the Monte 

 Diablo range with the thirty -fourth parallel of north latitude. The 

 length of the valley is about three hundred arid eighty miles in length 

 on an air line, with a breadth of fifty miles at its widest point. 



The general appearance of the valley is that of an extended plain 

 composed of alluvium, and this opinion would obtain in the mind of 

 any person whose line of travel should lead him over the lower terra 

 ces of the plain, or what is denominated its bottom lands. It is only 

 by making a transverse section of this plain that we should be able to 

 arrive at any correct conclusions of its structure, and peculiarities of its 

 formation ; by pursuing this course, very distinctive and marked fea 

 tures are observable of different periods of elevation to which this por 

 tion of the country has been subjected subsequent to its emergence 

 above the level of the sea. 



To arrive at a correct understanding of the formation of the " Cali 

 fornia Basin, "f we must first observe the rocks which form its borders, 

 their character, position and relative age ; and in doing this it will be 

 necessary to pass beyond either of its margins to ascertain the facts on 

 which an opinion may be founded. 



On the east side of the basin and at the distance of fourteen miles from 

 its border, we find the first out-crop of the primitive rocks, (granite) on 

 hills attaining an elevation of about one thousand feet above the sea. 

 Resting upon this, we find detached masses of sand-stone, which increase 

 to a well defined formation a few miles to the west ; immediately below 

 the latter a bed of slate makes its appearance, having a dip varying from 

 thirty degrees to nearly a vertical position, but as the lower hills are ap 

 proached, the inclination of these rocks become much less. Below the 

 slate, a conglomerate having an argelaceous cement is found, firm in its 

 texture, with a dip corresponding to the other rocks with which it is 

 associated ; the pebbles composing the conglomerate are quartz, jasper, 

 granite and trap ; at times this rock is highly ferruginous. The compo 

 nents of the rock are made up from rocks* found in the mountains to the 

 east, and must have been formed subsequent to the appearance of the older 

 trapean formations of this part of the country. 



Succeeding the conglomerate,^ which by way of distinction, we will 

 denominate Eocene, another bed of fissile cla}^ slate and aluminous clay 



* Col. J. C. Fremont. 



f Being similar to the London and Paris Basins, this name will be adopted. 

 \ This suite of rocks are often confounded with another group, of the same character which 

 appear of more recent date, and are found south of Consumnes river only. 



