BY G. THUBEAU, F.G.S. 5 



gendered electric currents" it becomes clear to the close and 

 careful observer of these tinique gold deposits, in situ, that 

 dynamical geology can alone account for these, strictly 

 speaking, volcanic j^roducts. 



Having myself had opportunities for examining active 

 " mud volcanoes " in 1877, near Carson City, State of Nevada, 

 U.S.A., these " Steamboat Springs " were most interesting, 

 and I can therefore speak with some authority upon the 

 subject. There, as is held by American geologists, these 

 volcanic "vents" occur on the line of continuation of the 

 famous Comstock Lode (silver-gold), and each spring or 

 geyser is indicated at the surface to the visitor, at a distance 

 by a thin column of white steam. When more closely 

 approached, it is found that the discharges of heated mud 

 and vapours are intermittent, and that previous to each of 

 such discharge a greyish semi-liquid mass rises slowly within 

 the mouth of the '* f umaroles " below, and en reaching the 

 top of the respective orifices, the carbonic, sulphu.retted and 

 other gases encompassed beneath, cause, through pressure, a 

 dome-like expansion of the " volcanic mud," which, however, 

 with increasing subterranean pressure eventually bursts, and 

 allows the " mud " again to subside. Each discharge, it is 

 noted, however, leaves a thin deposit or lamina in the "cups" 

 at the surface, which, after hardening, was found on analysis 

 to be chiefly charged with silica (quartz), and to also contain 

 a sensible percentage of gold and silver. This process is 

 even now in active progress, and as it assimilates a great deal 

 to what can be seen in its " dead state " at our " Iron Blow " 

 — if baryta is substituted for silica as matrix in the latter case 

 — the question of origin as to both metalliferous deposits is 

 not only, in my opinion, very suggestive, but forms the only 

 possibly true solution of the case. 



By way of further analogy, I would likewise draw attention 

 to the fact of Senor Santos having found "Lead" in the 

 "volcanic ash" from the eruption of Cotopaxi, of August 

 23rd, 1878, and in a paper read before the Eoval Society of 

 England, on January 6th, 1887, Mr. J. W. Mallet, M.D. and 

 F.R.S., etc., I'eports upon the " Occurrence of Silver in Volcanic 

 Ash, from the Eruption of Cotopaxi, Ecuador, of July 22nd 

 and 23rd, 1886." 



A condensed extract may prove of interest : — He, Dr. 

 Mallet, received a specimen of volcanic ash from Senor 

 Julian E. Santos, of Ecuador, which was collected at his 

 residence, Bahia de Caraguez, about 102 miles nearly due 

 west from Cotopaxi. This is the highest and most mighty 

 of the active volcanoes of our globe ; it erupted on the 22nd 

 ■of July, and the ash began to fall at Bahia de Caraguez next 

 morning, to a depth of several inches, thus representing an 



