CHEMISTRY. 223 



Precautions observed in assaying.— Tlie assavs tabulated at the end of Chapter III. 

 were made by my assistant, Mr. J. S. Curtis, who, in addition to a thorough 

 training, has had many years of experience in accurate and responsible 

 assaying. In attempting to detect minute quantities of precious metals in 

 the Washoe rocks, the first difficulty experienced was in obtaining suffi 

 ciently pure lead or litharge It was found that even that imported from 

 Germany and sold at a very high price as chemically pure was far too rich 

 in silver and too irregular in its silver contents to answer the purpose, lu 

 this dilemma Mr. Rickard, of the Richmond Mining and Smelting Company, in 

 Eureka, was kind enough to place a refining furnace with a new test at Mr. 

 Curtis's disposal, as well as the purest of the lead refined by the Luce & 

 Rozan process in the works under his charge. By careful manipulation Mr. 

 Curtis was able to prepare litharge assaying less than eight cents a ton and 

 of so regular a composition that, with the help of blank assays, the silver 

 contents of the rocks could be very exactly determined. 



A series of experiments was then made to determine the time of reduc- 

 tion which would give a maximum result with material so poor in metals 

 as the Washoe rocks. It was found that this time was much longer than 

 that requisite for the reduction of ore. Refined cream of tartar was the 

 reducing agent employed, with sodium bicarbonate and borax in carefully 

 determined proportions as fluxes. The cupels were made with great care 

 of two parts of bone-ash to one of cedar-ash, the surface being formed of 

 elutriated bone-ash. In cupelling feather-litharge was invariably allowed 

 to form, and throughout the experiments no known precaution was neg- 

 lected. 



Gold detected in the rocks.— In addition to the silver contents of the Washoe 

 rocks, gold also was detected, but in such minute quantities that little reliance 

 can be placed upon the relative tenor of different samples. It was estab- 

 lished, however, that the fresh diabase carries as much as four or five cents in 

 gold to the ton, and furthermore that the pyrite, so abundant in the decom- 

 posed rocks, carries both gold and silver, but more of the former than of the 

 latter. Thus pyrite washed from the decomposed diabase 250 feet north of 

 the C. &. C. connection with the North Latei-al of the Sutro Tunnel, assayed 

 three cents in silver and eight cents in gold, and pyrite from the Belcher 



