342 (,)ricKsiLVEi; deposits of the pacific slope. 



tliat crystalline silica, both fibrous and granular, forms from thermal springs 

 at the earth's surface. 



Gases. — Besides steam, hydrogen sulphide, carbonic anhydride, and 

 sidphurous anhydride escape from the springs and fissures. The quanti- 

 tative composition of the gas manifestly varies from point to point, and 

 therefore quantitative analyses were not made. In the qualitative anahses 

 free hydrogen and hydrocarbons were looked for, but none was detected. 

 Neither were oily hydrocarbons found here as they are at most quicksilver 

 deposits, though low forms of vegetation flourish in the waters of the hot 

 springs even at very high temperatures. The absence of hydrocarl)ons from 

 the gJises and deposits is a very important fact. The sinter rests upon 

 granite, and through this rock the spring-s reach the surface. If the hydro- 

 gen sulphide were a result of the reduction of soluble sulphates by organic 

 matter, hvdrocarljons would almost certainly be present, as was pointed 

 out b\* Bunsen in his great memoir on the geysers of Iceland. The com- 

 position of these gases, therefore, points to generation from inorganic 

 material at the seat of volcanic activity tar below the surface. Whether, 

 under the unknown conditions there prevailing, hydrogen sulphide can be 

 derived from sulphates without the intervention of organic matter b}' some 

 reaction not yet discovered, or whether the sulphur comes from regions 

 which have never been oxidized, is uncertain. The same gases are perceji- 

 tible at the mine as at the more active springs ; it is possible, however, that 

 a portion of the sulphurous anhydride at the mine is due to the decompo.si- 

 tion of hyposulphites. 



The metalliferous deposits. — The spHugs uow flowiiig emit 110 gTcat quantity 

 of water and many of the vents did not overflow at all during my visit; 

 neither does the water seem to be impelled toward the surface with any vio- 

 lence and in most cases it is perfectly clear. The mass of sinter through 

 which the water attains the surface is also many yards in thickness. The 

 deposits formed in the vents, particulai'lv when they are narrow cracks, con- 

 sequently consist of substances which have been held in solution by the 

 waters and which have been precipitated by cooling, evaporation, and, to 

 some extent, by acidification Large quantities of these deposits were col- 



