188 CALIFORNIA ACADEMY OF SCIENCES. 



or N. N. W. and S. S. E., and the dip very steep, somewhat 

 to the east; in comparatively few places, however, can either 

 be well observed. 



At the above-mentioned distance from Real there is a hot 

 spring, with a temperature of about 100^ F., containing very 

 little mineral salt but strongly impregnated with sulphuret- 

 ted hydrogen. Eastward the hills of the easterh^ range rise, 

 and on their slope the metamorphic series is traversed by a 

 great number of dikes of granite, porplmy or similar rocks. 

 This produces a peculiar effect, as the white dikes are visi- 

 ble from a long distance on the hillsides, running parallel 

 or sometimes intersecting each other like the meshes in a 

 network. A. short distance beyond this, granite appears to 

 begin again. The whole slate series is filled with quartz 

 veins, some of which contain gold; the larger of these veins 

 at Real run about east and west. The granite is usually 

 barren of gold. It is not known how far northward this 

 slate area of Real del Castillo extends, but it is probable 

 that it is entirely surrounded by granite, as extensive gran- 

 itic areas are seen in the mountains to the north. There are 

 several of these isolated slate areas in the northern part of 

 the peninsula and in San Diego County. So, for instance, 

 about fifteen miles east of Real, at the mining camp of Sara- 

 goza, according to statements of reliable informants at Real. 



However, one cannot fail to be impressed by the enor- 

 mous extent of the granite and the small areas occupied by 

 metamorphic rocks. It seems evident that the slates are of 

 but little depth and everywhere are resting, as detached 

 fragments, one might say swimming, on the granite. Of 

 the age of the metamorphic series, as found in or near San 

 Rafael valley, nothing more definite can be said than that 

 they are precretaceous, or at least older than the unaltered 

 and nearly undisturbed rocks of the Wallala Group. On 

 account of the extensive metamorphism it is not probable 

 that fossils will ever be found in them. I do not, however, 

 consider it improbable that they may be of the same age 



