16 NUMBER OF PARALLEL RANGES — TRANSVERSE DEPRESSION. 



Monterey, is divided into a series of parallel valleys by three well marked hill ranges, rnnning 

 southeast from the southern shores of San Pablo and Suisun bays, and from the Golden Gate. 



The most westerly of these is the Santa Cruz mountains, which, under the name of Monte 

 San Bruno and the Presidio hills, form the termination of the promontory on which San Fran- 

 cisco city is built. Lows hill at this point, as they pass south they increase in height, until, in 

 Santa Cruz and Santa Clara counties, they attain the average altitude of 2,000 feet. A single 

 hill in this chain, in San Francisco county, " Loma Prieto," reaches an altitude above that 

 point; but it is in Santa Clara county that these hills attain a continuous and lofty elevation, 

 which they preserve for the rest of their course south, until at the Pajaro river, near the 

 southern border of Santa Clara county, this range abruptly drops down. The total length of 

 this chain is about 85 miles, and the general strike is north 70° west ; a greater meridional 

 deviation than the chain lying immediately east has, whence it occurs that these two chains 

 approach each other, after travelling 70 miles parallel, and close up, by their approximation, 

 the Santa Clara valley, dividing it from the narrow valley of San Juan. 



The Santa Cruz range does not terminate, in a geological sense, at the Golden Gate, but is 

 found extending itself north of the strait or entrance of the bay, in which the islands of Alcatrez 

 and Los Angeles are its representatives, passing northwest along the shore oi Marin county and 

 dropping down terminates at Bodigo Head. Indeed, all the ranges found south of the bays 

 Suisun and San Pablo may be traced northward, forming by their elevation the valleys of 

 Napa, Petaluma, and Sonoma, until they terminate at Cape Mendocino. A great depression or 

 chasm has been produced across the strike of these ranges, by the exertion of volcanic forces 

 acting after they had been elevated ; and in the depressed valley running east and west, thus 

 produced, the waters of the ocean have advanced to meet the Sacramento and Joachim rivers, 

 which roll down their several valleys from opposite points. 



This great transverse depression of the whole land, from the ocean to the base of the Sierra 

 Nevada, along the parallel of 37° 31" north latitude, has assisted in making San Francisco 

 what she ever will remain ot these extreme western possessions. A similar transverse depres- 

 sion, between latitude 41° — 42°, has determined the course of the Klamath, and still further 

 north, in Oregon, a third depression is indicated by the Columbia river. Nor are these depres- 

 sions confined to the shores of the Pacific east of the Sierra Nevada. Humboldt river pursues 

 a course which cannot be said to be a true one, as its course is across the strike of the small 

 ranges ; and the Gila river has been adduced, in a later portion of this report, as a remarkable 

 example of a river which for many hundred miles pursues its course across the strike of moun- 

 tain ranges, forcing its way through caiions, and forming a course difficult to the traveller to 

 follow. 



From the southern shores of San Pablo and the Straits of Carquinez extends the second 

 range of coast mountains. These hills, like the former, are low toward their north extremity, 

 in Contra Costa county ; but rising gradually in Alameda county and Santa Clara, attain an 

 altitude equal to the Santa Cruz, which they almost join, near the mission San Juan, in Mon- 

 terey county. 



By this approximation of both ranges at the south, an acute angled triangle is formed, whose 

 sides are these hills, and the base occupied with the Bay of San Francisco, which, running up 

 into, terminates in Santa Clara valley, forming the apex of the triangle. 



East of this second range lies an elevated undulating country, hill and vale, extending fifteen 

 to twenty miles, until the Monte Diablo range is reached. This third range, so called from 



