446 
POPULAR SCIENCE REVIEW. 
of gold being all sandstones, clays, slate, and grits belonging to 
tbe Palaeozoic period. So muck for tbe strata which produce 
the gold. Now we have to consider the position in which the 
metal is found and worked ; and at the very outset we arrive at 
a practical conclusion — one which has been attained by many, 
many failures, and much bitter experience, viz., that it seldom 
or never pays to sink shafts for gold, since it has been proved hi 
all the auriferous districts, that the richest find will be at the 
surface, and that the lower the adventurers sink the poorer in 
quality and less bountiful in supply becomes the precious 
metal. 
The natural question then arises, as to the position of these 
drifts which have yielded so much gold and made so many for- 
tunes. Let us, therefore, go back for a moment to the Oural 
Mountains. Sir Roderick tells us that the chief source of the 
metal is the accumulation of drift on the sides of the mountain, 
or the alluvium of the water-courses which descend to the 
valleys through the gullies ; and the reason of it is this : — We 
must imagine a number of peaks and ridges permeated with 
intrusions of porpliyritic rocks, &c., and impregnated with gold. 
Denudation has largely taken place at one time or another, 
so that the outlines of these ridges have become altered, and 
a large quantity of material carried away and ground down to 
detritus of different sizes. It happens that, in the Oural chains 
particularly, we can fix the date of this grinding or denuding 
action, viz., at the period of the great glacial drift — a compara- 
tively recent period, in which, nevertheless, the whole of the nor- 
thern countries of Europe and Asia were permanently altered, 
from the ineffaceable quantities of material carried southward by 
the waters and icebergs of this Arctic period. We know, also, 
that what are now the northern portions of the continents were 
then inhabited by a singular kind of elephant and mammoth, 
adapted to the severity of the climate in which they lived ; and 
accordingly associated with the heaps of gold-bearing’ detritus 
in the Ourals are found bones of these extinct animals, prov- 
ing beyond all doubt the age of the drift. It is, therefore, not 
difficult to imagine why it is that these superficial gold-drifts 
are the richest, because not only do they bear in then bosom 
the materials from the surface of the veins which we have 
already seen is the most valuable, but the expense and labour 
of extracting and working the gold are as nothing compared with 
the expense of sinking shafts into the solid rock. Indeed, so 
well is this understood, that there is only one locality in the 
Siberian chain worked sub-terra, and that very sparingly. In 
Australia we find the same broad features, viz., that the gold- 
fields are in reality drifts of gold derived from the slaty pri- 
mary rocks, and that the immense treasures extracted from them 
