282 Scientific Proceedings, Royal Dublin Society, 



ochre found in the cavities of the nuggets. The specific gravity 

 of the specimens varied from 12, that of the largest nugget, to 16, 

 that of the fine grains, although the gold was 22 carats fine. The 

 specific gravity of fine gold being 19*4, that of gold of the compo- 

 sition of that of Wicklow should be about 18. 



While considering what is to be inferred from the distribution 

 of the gold in the valleys, it is well to remember that the deposit 

 in which it occurs is a recent one, and that the several water 

 basins were necessarily, during the deposition of the gravels, very 

 similar in extent and configuration to what they are at present ; 

 also, that at least towards the close of the period, the general 

 features of the district were like what they are now, except per- 

 haps a little more rugged and steep. The principal changes that 

 have taken place since then, being a rounding and smoothing 

 down of the hills and a filling up, especially the lower parts, of 

 the valley. 



From the nature of the gravel and the worn surfaces of 

 the underlying rock, it is evident that a rapid current flowed 

 down these valleys at some former period. Although the gold 

 and associated minerals are now most abundant at the bottom of 

 the gravel, it is not necessary that they should be deposited first 

 — while the upper and poorer portions accumulated at a later 

 time — because while the gravels were thoroughly fiooded with 

 water, the natural tendency of the finest and heaviest portions 

 would have been to work their way downward towards the bed 

 rock ; and during heavy floods, the lighter portions on the surface 

 would be carried forward, leaving the heavier higher up the 

 stream. 



The gravels in the lower lying portions of the adjoining valleys 

 show that at one time these were estuaries ; but as no sinkings 

 have been made in the deep gravels of the auriferous streams, it 

 is impossible to say whether they were estuarine or not when 

 the deposition of the gold took place in the upper reaches. 



The occurrence of the largest pieces of gold, with a greatest 

 abundance of the associated mineral substances, particularly the 

 tinstone, below certain points on each of the streams, above which 

 they were either absent altogether or only traces of gold were to be 

 found without the usually accompanying minerals, suggests each 

 of these places being in the neighbourhood of the lode. Further- 



