Alluvial Gold Drifts . 
131 
combined with the results of further denudation of the Silurian 
rock-masses. A considerable portion of the materials now com- 
posing the Upper and Post Tertiary gravels, and the gold associated 
with them, may have once formed part successively of. Upper 
Palaeozoic, Mesozoic, and Lower and Middle Tertiary detrital 
deposits ; denudation during each succeeding period having sifted 
and re-arranged the materials, removing the soft and friable, 
leaving the harder fragments more and more water worn, and 
making further encroachments on the Silurian rocks. Throughout 
all changes, however, the larger disintegrated particles of gold, 
owing to the high specific gravity of the metal, appear to. have 
been conveyed to but comparatively short distances from the 
parent quartz-lodes. Once freed from its matrix, the natural 
tendency of a fragment of gold of any appreciable weight is 
merely to drop deeper, as the surrounding or subjacent materials 
are removed, and though much of the gold in the leads has 
probably travelled for some distance, it appears to have done so 
principally while attached to portion of its matrix, or when in 
small particles in company with masses of other materials which 
carried it along with them ; or when a smooth bed-rock offered 
no resting place. 
On this circumstance may be founded a principle that, where 
there are auriferous alluviums, there are likely to be auriferous 
quartz-veins at no great distance. Though by no means new, 
this principle has not hitherto been recognised in its full import- 
ance, and there is reason to believe that its judicious application to 
extensive and systematic prospecting would result in a largely 
increased development of quartz-mining throughout the colony. 
