I9I0.] COAST RANGES OF CALIFORNIA. 327 



found to the east of the road from Lakeport to Glenalpine about 

 one mile from the latter place. 



The serpentine of these areas occupies low dome-shaped hills, 

 over which numerous boulders of the rock ranging in diameter 

 from one to three feet are strewn. From dark green to greenish 

 blue they show the typical Iherzolite serpentine in all its stages of 

 decomposition. 



III. The Mayacmas District Serpextines. 



A narrow strip of serpentine extends in a northwest direction for 

 about twenty-four miles, following more or less closely the ^Nlayac- 

 mas range. It is very irregular in shape. 



Near yEtna Springs are found a number of small areas with 

 low outcrops which seem to form a connecting link with the Pope 

 Valley serpentine and the Mayacmas area. Beginning at the 

 yEtna Mine a narrow belt can be traced to the northwest by a num- 

 ber of quicksilver mines, the Twin Peak, Corona, Mirabel and Great 

 Western Mines which are situated on its contact. The outcrops are 

 very low along this belt. The contact, which is with a sandstone in 

 the north, is partly with a basalt, partly with a sandstone in the 

 south. Brush and soil cover it and only occasional outcrops indi- 

 cate the general direction of the serpentine. The width of the belt 

 varies. At places it is a hundred feet wide, but never more than 

 one half a mile. Several narrow bands branch off to the south 

 approaching ]\Iount St. Helena. 



At the Great Western Mine the belt assumes greater dimensions. 

 It becomes more than a mile wide and forms the crest of the Alayac- 

 mas range, which here has an altitude of 2,900 feet and gradually 

 rises as Pine Mountain is approached to 3,500 feet. At Pine ]\Ioun- 

 tain the Mayacmas range divides into three branches, all extending 

 in a northwest direction. The most southern one consists of a series 

 of ridges and peaks of which Geyser peak is best known. The Big 

 Sulphur or Pluton Creek cuts a steep canyon on its northern flank, 

 forming a dividing line with that range of which Mount Cobb is the 

 highest point looming to a height of 4,500 feet into the skies. The 

 range furthest north is not continuous with the Mayacmas range. 

 Putah Creek cuts a deep canyon which isolates it. It reaches an 



