186 CALIFORNIA ACADEMY OF SCIENCES. 



joining the granite are coarse- to middle - grained diaba- 

 ses. Before reaching the first divide granite appears again, 

 but tlie metamorphic is seen to continue, covering the 

 granite for some little distance north of the road. How far 

 this metamorphic belt reaches is not certain, but the pro- 

 bability is that it continues for quite a long distance south- 

 ward. No quartz veins are seen in this zone, nor have any 

 placers been reported from this neighborhood. 



Granite forms the summit of the first range, and rises in 

 naked clifi*s a few hundred feet above the pass (2,500 feet) 

 to the north and south of the road; it continues forming 

 the divide, northward, at least till opposite Real del Cas- 

 tillo. 



From the summit of the pass the view is extensive and 

 beautiful. Six or seven hundred feet below lies the 

 largest of the interior valleys, Yalle de San Rafael, a basin- 

 like depression about fifteen miles long north to south, 

 and ten miles from east to west. On all sides it is surrounded 

 by mountains, mostly bare, light-colored granitic ranges; the 

 highest range, forming the main divide between the Pacific 

 and the Gulf, rises directly eastward, and its summit forms 

 a gently undulating sky line far away. 



The irregular series of depressions to which the name of 

 " the interior valleys" has been given, runs approximately 

 north and south, and at a distance of about twenty or thirty 

 miles from the coast. Northward it is represented by Valle 

 de las Palmas and Guadaloupe; southward it continues in 

 the valleys of Santa Clara, Santa Catarina, and Santa Cata- 

 lina; all these are separated by more or less prominent trans- 

 verse ranges, and are situated at somewhat differing eleva- 

 tions, from 1,500 to 3,000 feet, but that they should be re- 

 garded, all together, as a result of the same or similar geo- 

 logical causes appears very probable. 



San Rafael Valley is topographically somewhat peculiar, 

 as it is formed by two rivers, the San Carlos and the Guada- 

 loupe, the former fiowing through the southern, the latter 



