30 



Transactions. 



source of the metals. The source may not be deep-seated, 

 but that it exists at some distance below the flow of basalt is 

 almost certain. 



The waters of the Ohaeawai springs were found bv Captain 

 Hutton in 1870 to contain zinc, manganese, silica," free sul- 

 phuric and hydrochloric acids, but not traces of mercury.'- A 

 sample of the water analysed by W. Skey in 1896 gave the 



following results :— 



Protoxide of iron 



Lime 



Magnesia ... 



Silica 



Sulphuric acid 



Hydrochloric acid 



Sulphuretted hydrogen 



Alkalies 



Ammonia ... 



Organic matter 



Grains 



per Gallon. 



2-23 



5-97 



115 



310 



13-60 



66-91 



Traces 



41-66 



Traces 



Traces 



Comstock Lode. 



Abundant evidence of the hydro-thermal origin of veins 

 traversing eruptive rocks is also obtainable in Europe and 

 America. 



In several of the mines in the Comstock Lode ascending 

 thermal waters were encountered in the deep workings, and 

 seriously impeded mining operations. t The water which 

 flooded the Gold Hill mines issued from a borehole in the 

 Yellow Jacket Shaft at a depth of 3,080 ft. It had a temper- 

 ature of 170° Fahr., and was heavily charged with hydrogen- 

 sulphide.]: 



Baron von Richthofen,§ who examined the Comstock Lode 

 at a time when no abnormal temperature was noticeable, 

 ascribed the origin of the lode to earlier solfataric action. 



Sulphur Bank Cinnabar-deposits. 

 The quicksilver - mines at Sulphur Bank, in California, 

 furnish important evidence in relation to the genesis of ore- 

 deposits by solfataric action. At this place the basements 

 rocks are slates and sandstones overlain bv a fresh-water 



* F. W. Hutton, " On the Occurrence of Native Mercury near 

 Pakaraka, Bay of Islands," Trans. N.Z. Inst., vol. iii, 1871, p. 251. 



•f Clarence King, U.S. Geological Exploration of Fortieth Parallel, 

 1870, p. 87. 



I George F. Becker, " Geology of the Comstock Lode," U.S. Geol. 

 Surv. 1882, p. 230. 



§ F. von Richthofen, " The Comstock Lode, its Character and Pro- 

 bable Mode of Continuance in Depth," San Francisco, 1866, p. 54. 



