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TRANSACTIONS OF THE SECTIONS. 61 
tritus of the latter deposits contain no traces of gold, though they abound in copper 
ores, it was pointed out by the author in his work on Russia, that the auriferous 
veins were there posterior to those of iron and copper, and must have been produced 
after the accumulation of the Permian system. 
Exhibiting maps, sections and views of the Ural Mountains, formerly prepared by 
him, and referring to the description of California by Erman and others, he entered 
upon a comparison between the two countries, and showed that there were great coinci- 
dences of mineralogical structure in both, and that with these constants the same 
results obtained in America as in the Ural; the chief distinction consisting in the 
apparently larger proportion of gold in the detritus of the newly-discovered deposits of 
California than in those of the Ural. He contended, however, that no very large tract 
of California would be found to be as uniformly auriferous as the banks and slopes of 
the upper tributaries of the Sacramento. That gold ore has been found in certain 
localities along the western slope of the Sierra Nevada is admitted, but its conti- 
nuity as well as the breadth of the deposit have yet to be ascertained. 
And here the author took some pains to indicate the distinction between all such 
surface operations as those of Siberia, California, and the Brazils, and those works 
in which, besides the ores of silver, copper, &c., gold also had been extracted from 
veins in the solid or parent rock; the latter operation being very seldom remunera- 
tive. Adverting to the fact, that in the Ural Mountains the veinstones “in situ” (in 
this case little or no admixture with other ore exists) have proved very slightly remu- 
nerative when worked further downwards, he glanced at an opinion of Humboldt, who 
looking to the great lumps or ‘‘ pepites” occasionally found in the surface rubbish, sup- 
posed that there may have been some connection between the production of gold and 
the atmosphere ; since judging from these specimens, it was from the superficial extre- 
mity of these quartz veins that the richest bunches of gold must have been derived ; the 
veinstones when followed downwards having invariably proved either sterile or very 
slightly productive. 
The author carefully distinguishes the major part of the auriferous detritus from 
modern alluvia, and shows that it has been the result of former and more powerful 
causes of degradation than those now in operation—causes which distributed coarse 
shingle, blocks and sand, and which wearing away all the associated schists and 
the most oxidizable ores, left only the harder rocks, particularly the quartz veins, 
together with the harder and nobler metals gold and platinum. The existing rivers 
have had little more to do with this phenomenon than that in mountainous tracts ; 
and where they have a rapid descent, they have occasionally laid bare the edge of the 
previously-formed and water-worn gold accumulations. By this observation it is not 
meant to deny, that where existing streams flow directly from rocks “in situ” which 
are now impregnated with gold, a little auriferous detritus must not naturally be 
washed down, but simply to prevent the student who may refer to detailed maps of 
gold tracts from imagining that the rivers are auriferous, except where they derive 
that quality from the wearing away and breaking down of the mixed materials 
which constitute their ancient banks. Ina word, British geologists may be assured 
that gold shingle and sand have been accumulated just in the same manner as the 
former great drifts of their own country, whether general or local, in which bones of 
the fossil elephant, rhinoceros, and other extinct quadrupeds occur. 
Having terminated his account of the geological constants which accompany gold 
mines in Europe, :\sia and America, Sir Roderick then traced the history of gold and 
its development, as known to the ancients and our ancestors of the middle ages. He 
showed that in all regions where the above-mentioned paleozoic, crystalline and 
eruptive rocks occurred, gold had been found in greater or less quantities, and that 
just in proportion to the time a country had been civilized, the extraction of the pre- 
cious metal had diminished; so that in many tracts, as in Bohemia, where gold had 
formerly prevailed to a great extent, it had been worked out and the mines forgotten. 
Briefly alluding to the examples at home of gold-works in Wales under the Romans, 
where Silurian rocks are pierced by trap, and contain pyritous veinstones as described 
by himself*, and to the former gold of Scotland and Ireland in similar rocks, its oc- 
casional discovery still in the detritus of the county of Wicklow, and its diffusion in 
* Silurian System, p. 367. 
