448 QUICKSILVER DEPOSITS OF THE rACIFIC SLOPE. 



em edge of the deposits. Tlie quantity of quicksilver at their eastern edge, 

 where the principal active springs now exist, is ver)- minute, and this may be 

 due to the composition of the underlying granite. Now, the granite subjected 

 to analysis was collected about half a mile still farther east than the active 

 springs, and consequently a mile and a half from the mine If the granite 

 contains quicksilver, but in diminishing quantities as one proceeds to the 

 east, it might well be that the quantity at this point would be imperceptible. 

 On the other hand, it might be argued that the presence of antimony, arsenic, 

 lead, and copper in both the granite and the spring deposits is a mere coin- 

 cidence, that the infragranitic source of the ore has been gradually ex- 

 hausted, and that consequently only the older deposits show considerable 

 quantities of mercury. This argument would not, however, quite fit the 

 facts, for, while steam and hot gases still issue in small rpuintities from the 

 mine, there is a belt ojf solfataric matter at the very eastern edge of area 

 mapped at Steamboat. The springs here were evidently a portion of the 

 same system now active, but hei'e neither water nor steam now issues. 

 These eastern springs were the oldest of the group, yet no trace of quick- 

 silver has ever been detected in the decomposed mass. If the quicksilver 

 were derived from a limited infragranitic source, these eastern localities 

 should show ore more abundantly than an^- other. 



Comparison between Steamboat and the Comstock A COmparisOU liaS beCn Uiadc 



on page 352 between the character of the deposit of Steamboat Springs and 

 that of the Comstock lode, six miles distant, which is also significant in the 

 present connection. The hanging wall of the Comstock is diabase,^ and 

 I have adduced mucii evidence going to prove that the main source of the 

 ore in this lode is this Pre-Tertiary eruptive mass, from which it was ex- 

 tracted by intensely hot waters rising from great depths, charged with sul- 

 phides and carbonates of the alkalis.^ 



' See Geology of the Comstock Lode aud Bull. California Acal. Sci. No. 6, 1886, p. 94. 



'Prof. J. S. Newberry bas made a curious criticism of my theory of the ore deposition ou the Com- 

 stock (School of Mines Quarterly, vol. 5, 1884, p. 338). He s.ays: "Richthofeu, who first made a study 

 of the Comstock lode, suggested that the mineral impregnation of the vein was the result of a process 

 like that described, viz, the leaching of the deep-seated rocks, perhaps the same that inclose the vein 

 above, by highly heated solutions, which deposited their load near the surface. On the other hand, 

 Becker supposes the concentratiou to have been effected by surface waters flon-ing laterally through the 

 igneous rocks, gathering the precious metals and depositing them in the fissure." The inaccuracy of this 

 statement may be seen from the following qnotatious. Baron Richlbofen writes (see The Comstock Lode : 

 Its Character etc. or Mon. U. S. Geol. .Suivey No. 3, p. I'.l) : '' Kliioriur and chlorine arc the most power- 



