.MIXES IX AXDKSITR. 245 



detritus. Were it a crater anything- like so old as the mass of the mountain, 

 an outlet would almost (-ertainly have been cut through the low swell of 

 land separating- it ivom Clear liake on the east and much material nuist 

 have fallen into the basin from the perpendicular cliffs of columnar aiidesite 

 to the south. On the other hand, there seems to have been no outflow of 

 lava, either andesitic or Ijasaltic, from this basin. There is, moreover, evi- 

 dence that Elgin Point has been considerably raised m very recent times, 

 and it appears probable that the basin of liittle Borax Lake was formed by 

 an explosive outburst, which was nearly or quite contemporaneous with the 

 basalt eruptions to the southeast. A partial renewal of volcanic activity 

 on the old line of eruption at a period of volcanic disturbances in the im- 

 mediate neighborhood is certainly nothing to be wondered at. The origin 

 of the borax in this lake is no doubt entirely similar to that of the borax in 

 the other and more important lake near Sulphur Bank, which will be dis- 

 cussed in the next chapter. There are now no hot spring's flowing into it, 

 though there are warm springs associated with the andesite at several other 

 points. 



Quicksilver deposits in andesite. At tWO loCalitlcS OU tllC SOUtliem sidc of Mt. 



Konocti cinnabar has Ijeen found. One of these is close to the base and 

 was known as the Bowers mine. It is abandoned, and all that could be 

 made out from the accessible workings was that the associated andesite is 

 quartzose and is bleached by solfataric action. The Uncle Sam mine is high 

 up on the flank of the mountain. It, too, is in dacite, much decomposed, as 

 if by the action of heated waters or gases. A considerable quantity of 

 ore was formerly extracted at this point and sold to the Sulphur Bank 

 Company, but statistics were not obtainable. 



It is possible that the dacite eruptions were later than the mass of the 

 mountain and that the solfataric action accompanying the outflows of this 

 rock induced the deposition of ore, but no conclusion on this subject was 

 reached. It is certainly remarkable that the only dacite occurrences known 

 in the district are thus associated with the only quicksilver deposits known 

 among the andesites. 



Basaltic eruptions. — Tlic eruptious of Ijasalt of the Clear Lake region Avere 

 greatly inferior in volumo to those of andesite, even more so than would 



