36 On the Geological Distribution of Gold. 



During the course of the turbulent era of denudation, 

 we have every reason to suppose that all attainable rocks, 

 whether auriferous or not, were exposed to the violence and 

 destructive agencies of the epoch, and naturally worn down, 

 when the gold-bearing shared the fate of the rest of the rocks, 

 being equally exposed to the process of disintegration and 

 idtimate denudation. And when we reflect on the fact of 

 all such rocks being left in a bare or denuded state, we may 

 also imagine that the volume of water which apparently per- 

 formed the work of gathering and carrying off all which 

 came within the reach of its mighty moving force, was 

 transported by the' existing outlets and accumulated on the 

 bed of the ocean. The probability of certain reservoirs or 

 natural dams, as already alluded to, may be viewed as a fact 

 in many localities, by which means some of the materials of 

 denudation were retained for further distribution. After 

 all, it seems very difficult to form an idea as to the modus 

 operandi by which the desintegrated matter during the 

 denudation became stored for ulterior use. 



Where gold-bearing veins have apparently made their 

 appearance posterior to the early periods of the tertiaries, 

 there we have no reason to expect gold as originating from 

 the rock. Veins existing in stratified rocks may have 

 undergone a change in position, as the rock itself, viz., 

 been tdted up from a horizontal to that of a more or less 

 vertical position, and if the materials forming the veinstone 

 were deposited when the rock existed in this position, such, 

 would facilitate our ideas about the formation of metal- 

 liferous veins. The alteration from a horizontal to a more 

 or less inclined position might have taken place at a period 

 posterior to the epoch of the denudation of the rock itself ? 



Stratified vein-stone, carrying gold, is seen in several local- 

 ities in South America. A rather singular instance of a 

 stratified quartz-layer, being auriferous, is seen in Antioquia, 

 where an undulated stratum of quartz rests on the granite, 

 the superior portion of the same being covered with 

 fluvial detritus, partly productive of gold. This stratified 

 quartz was here deposited on the bare granite, consequently 

 posterior to the epoch of denudation. 



That many auriferous veins existed previous to the last 

 denudation, there can be no doubt; but that all such veins were 

 prior to the catastrophe of denudation, is a question which 

 remains stdl unsolved. The answer may be expected at 

 some future day. 



