142 



University of California. 



[Vol. 2. 



been carried up, and to some extent, sorted by the winds. Along 

 the greater portion of the coast, which is low and rolling, these 

 sands are the ordinary beach sands extending inland for a mile or 

 more, but at two or three points they have a different character, 

 and a considerably greater thickness. 



At the Pierce Ranch, and still farther north on Tomales Point, 

 there are deposits of fine sand having a brownish color and a much 

 firmer bedding than ordinary beach sand. The short, deep ravines 

 cutting down through them show depths of more than one hundred 

 feet, and appear not to have reached bed-rock at that depth. They 

 contain veins and streaks of iron oxide that have been segregated 

 by the action of the surface water, and these veins stand out in 

 relief upon the faces of the steep sides of the ravines. The eleva- 

 tion of the surface of these sand deposits above sea level is about 

 300 feet at their highest point. At the northern end of the ocean 

 beach, near the lighthouse enclosures, there are similar deposits 

 of about the same depth and elevation. They consist of the finer 

 and lighter material of the beach wash, which has been carried up 

 by the winds to higher levels. 



Overwash Gravels. — Deposits resulting from recent atmospheric 

 erosion are not uncommon, and may sometimes be mistaken for the 

 terrace gravels already described. They occur along the lower 

 slopes of the hills and cap some of the sea-cliffs to the east of 

 Drake's Bay. They have not the regular stratification, though, of 

 marine deposits, and so far as observed have no considerable 

 thickness. 



Geology of the Farallone Islands. — According to Mr. J. W. 

 Blankinship, 1 formerly a student of the University of California, 

 who visited those islands with Charles A. Keeler, the geology 

 of the Farallones is quite similar to that of the promontory of Point 

 Reyes, being that of a basement of granitic rocks overlain by mass- 

 ive beds of heavy conglomerate. The conglomerate is found along 

 the northern and western sides of the group and was thought 

 to dip northward. Distinct terraces were found surrounding the 

 larger island, but at a lower level than any that were observed 



1 Zoe, Vol. 3, 1892, p. 145. 



