119 



been derived from their pre-existing upper surfaces." Tliough. 

 Mr. Brougli Smyth has represented, in the " First Sketch 

 of a Geological Map of Australia," 1875, published under 

 the authority of the Victorian Government, our metalliferous 

 rocks as belonging to the same period of time as the gold- 

 bearing Lower Silurian rocks of Victoria, yet this is only 

 one of the many inaccuracies which render the South Aus- 

 tralian portion of that map almost valueless. Elsewhere it has 

 been shown that our metalliferous rocks are overlain uncon- 

 formably by fossiliferous rocks of Lower Silurian age, and 

 therefore they must belong to a vastly older formation.'^ From 

 the circumstance of their inferior stratigraphical ])osition to 

 the Lower Silurian we have applied to them the tentative 

 designation " Pre-Silurian." 



Secondly, as to dissimilarity of character. In Victoria the 

 auriferous reefs consist mostly of massive white quartz, and 

 are plainly exposed on the surface. The active and sanguine 

 spirit of enterprise which has been exhibited by the mining 

 community of Victoria in the last few years has been well re- 

 warded by the discovery of auriferous reefs and drifts beneath 

 the basaltic cover in the Ballarat, Clunes, and Creswick dis- 

 tricts. There reefs abound all through the gold-fields ; but, as 

 it is commonly said, ninety- nine in a hundred prove barren ; 

 however, the hundredth one carries gold throughout its mass. 

 Here the reefs are more frequently of a mullocky character, 

 and are more or less covered by detrital matter ; iron ores 

 largely prevail, and often those of manganese, intermixed with 

 the quartz, whilst the gold is fitfully distributed in the matrix, 

 though most quartz reefs hitherto explored have proved to 

 contain some gold. Thus, from a general comparison between 

 this colony and Victoria as to the facilities of prospecting 

 for, and the chances of the existence of, remunerative gold 

 reefs, I must say that there are serious obstacles, arising from 

 the dissimilarity of character of the veins, and from the widely 

 different ages of the strata. But the occasion for an earnest 

 study of the question. Is the distribution of reef -gold limited 

 in depth ? is as yet far distant, seeing that we have not yet 

 satisfied ourselves as to its persistency near to the surface. 



Examining our auriferous veins per se, their characteristics 

 point to the probability that the gold occurs more abundantly near 

 to the surface, especially so in the case of the veins charged 

 with iron pyrites. Iron pyrites I have experimentally deter- 

 mined to be a solvent for gold, in the same way that iron is for 

 carbon, as in cast-iron. By access of moist air the iron pyrites 



* Mihi, Trans. Eoy. Soc. S. Aust. II., p. xiv. ; Tepper, id. pp. 76-77 ; 

 Scoular, id. vol. III., p. 112. 



