340 A. LIVERSIDGE. 
substance (such as might be met with under natural circumstances) 
would increase in weight, this has been answered in the affirma- 
tive, and I think we can safely say that a nucleus of gold in an 
alluvial deposit or in a vein in contact with any of the foregoing 
substances or other similar bodies, would tend to increase in size 
so long as the supply of gold in solution was maintained, and 
that masses as large as the largest known nuggets, or indefinitely 
larger, might be so formed. My own opinion, however, in spite 
of this is that the large nuggets have not been so formed, but 
have been set free from veins, and have acquired their rounded 
and mammillated surfaces by attrition ; the main outline being 
due to the original form of the mass when liberated from its matrix. 
Nuggets may have also received deposits of gold from solution, but 
such deposits have I think made no material alteration in the size 
of the larger nuggets. 
The advocates of the hypothesis is that the large nuggets have 
been formed in situ, support it by the following amongst other 
arguments :— 
1. That the large nuggets have been found to have a different 
chemical composition to the vein gold. 
Undue weight seems to have been attached to this, the dis- 
similarity in composition between nuggets and vein gold is usually 
but small and immaterial, and sometimes the vein gold is even 
richer than the alluvial. The variations certainly do not show 
that the nuggets have necessarily had a different origin. 
With finely divided alluvial gold there is a greater difference 
in composition, this may be due to the silver and other impurities 
having been partly removed by solution, the greater surface 
exposed by the gold dust and grains would of course facilitate 
their elimination. 
2. That the large nuggets have all been found far removed from 
the nearest vein. This is an argument of no great importance ; 
and it is already answered in the preceding pages; the reef from 
which they have been derived may have been entirely denuded 
away or so covered with other material as to be inaccessible. 
