400 Transactions op the 



are located is known as the Mount Diablo Range. Just west of the peak 

 from which the range takes its name, lie the Straits of Carquinez, 

 through which the waters of the Sacramento and San Joaquin force 

 their way and enter the Bay of San Pablo. West of the Straits the 

 mountains trend to the northwest, gradually increasing in altitude. 

 The}* form the watershed between the Sacramento and the valleys 

 west of it to the Pacific Ocean. Napa Valley lies between the main 

 range and a spur from it terminating on San Pablo Bay. The great 

 vallej's of Sonoma County are formed by another spur from the same 

 range, terminating on San Pablo Bay at a point further west. This last 

 spur forks and forms two valleys, Sonoma and Petaluma, both with a 

 delta and frontage on the Bay of San Pablo. All these spurs unite 

 with the main range, which then passes through the northeastern cor- 

 ner of this county. At or near this point of intersection a rich body of 

 quicksilver is now being developed, a deposit which bids fair to equal if 

 not surpass the greatest in either the old or new world. 



A number of mines had been opened and successfully worked in the 

 main range southeast of where it enters Sonoma County. Prospectors 

 traced the croppings of the ledges along the range into this county. 

 Granville and Green Thompson located a claim in eighteen hundred and 

 seventy-two. They discovered large deposits of float ore and took up a 

 claim called the Sonoma. This claim was sold to a San Francisco firm 

 who immediately built a furnace and, by November of the same year, 

 were reducing metal. The mine has been worked steadilj", yielding a 

 regular monthly supply of quicksilver. An excitement followed; a 

 great, number of claims were located and rich discoveries were made. 

 A mining town sprang up, and Sonoma County, which had long ranked 

 as one of the finest agricultural counties in the State, was discovered 

 to have a mining interest second only to her great wealth in wine, wool, 

 fruit, dairy products, and wheat. 



This mineral district is located in the northeastern corner of the 

 county, in the hills forming the eastern boundary of upper Russian River 

 Yalley. They are about fifteen miles from Healdsburg and twenty- 

 seven from Santa Rosa. The mountain district in which they are 

 located is about twenty miles long by an average width of about ten 

 miles, including the main range and the spurs from it. Two bold 

 streams rise in the main range. They flow in a northwest direction, 

 with the trend of the mountains, on either side of an immense spur 

 from the main range, unite and empty into Russian River, near the 

 northern boundary line of the county. The highest point in this spur is 

 Geyser Mountain, a rounded and beautiful peak, visible from all parts of 

 the great valleys of Sonoma. It takes its name from the famous Geyser 

 Springs, which send up their wonderful columns of steam from a deep 

 gorge, of which this spur is the western wall. In this range are located 

 some very valuable mines. Among the most prominent are the Socrates, 

 the Flagstaff, the Sonoma, the Anna Belcher, the Rattlesnake, the Mis- 

 souri, the Oakland, and the Geyser. We mention these as they are pro- 

 ductive — all having furnaces now running, or about to commence — and 

 with no desire to draw invidious comparisons or to disparage other 

 claims. There is one peculiarity worthy of mention: those mines near- 

 est the Ge} r ser steam springs produce free mercury, the Socrates, the 

 Flagstaff, and the Rattlesnake; while those further distant produce cin- 

 nabar, which is a combination of mercury and sulphur. It is not im- 

 probable that the mines will yield during the coming Summer from one 

 thousand to one thousaud five hundred flasks of metal a month, worth 



