Doc. No. 9.] 13 



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as marked and distinct as their geographical position and vegetable 

 productions, while the courses which both pursue are widely variant, 

 forming an angle of thirty-six degrees in ninety-one miles. For local 

 convenience of description this division should be made, if for no other 

 reason. 



A division, or rather a new arrangement, is to be introduced in rela 

 tion to the entire mountain chains that lie upon the west side of the con 

 tinent, which will give more uniformity and a much better classification 

 than that now existing. It is not proposed however to change local 

 names in the arrangement, but to name those parts of the mountains, 

 which, as yet, have received none, except " Sierras," as they are termed. 

 Through Mr. Blake, of the U. S. E. E. Survey, I am informed that it is 

 now proposed to term the entire chain of mountains, extending through 

 to the northern part of Oregon, and running south into lower California, 

 " Cordilleras or Western America," and all those portions south of the 

 thirty-fifth parallel of north latitude, [which, as yet, have received no 

 name,] are to be termed the " Peninsula range" in order to separate them 

 from the coast mountains with which they are now often confounded, 

 and again as often termed Sierra Nevada, by persons who have occasion 

 to describe them, or any part of them. 



The terms "Sierra Nevada," and "Cascade Eange," will thus be re 

 tained as local names, with their boundaries the same as before. The coast 

 mountains will comprise the entire chain lying to the west of the above, 

 and which are found to have an age more recent than the tertiary rocks, 

 which rest upon them, and such local changes as may be necessary will 

 be applied, but so far only as will be required in order to elucidate any 

 peculiar characteristics they may possess. 



This arrangement is one much needed, and is founded on strictly sci 

 entific principles, and this proposition of Mr. Blake will meet the uni 

 versal concurrence of the country, as it will reduce the mountain chains 

 of the western part of the continent, to a more perfect system than they 

 have heretofore possessed. 



A more specific classification of these mountains has before been pro 

 posed by different persons, among them that of Lieut. Wilkes, who pro 

 posed the term of " California Eange of the Cascades;" for the Sierra 

 Nevada being but a continuation of the former, all of them heretofore 

 have been objectionable on the ground that old and established names 

 would be changed by the arrangement ; notwithstanding those names con 

 veyed erroneous impressions. No such objection can be urged against 

 the present proposition of the gentleman above named, as it affords a 

 convenience of arrangement not heretofore suggested or presented to the 

 public for their consideration. With these remarks on this part of our 

 subject, we will proceed to the examination of the chain termed the 

 Monte Diabolo Eange. 



GEOLOGY OF THE MONTE DIABOLO EANGE. 



This chain of mountains forms the south shore of the Straits Carquinez 

 and part of the bay of Suissun. The rocks bordering the bay and straits 



