660 
DESCRIPTION OF THE MAPS IN VOL. I. 
consult the local maps prepared by the different officers of the Imperial School of Mines 
alluded to in the text, in relation to the districts around different centres of mining 
operations. But, after all, the spaces being considerable, concerning which we have no 
information to be depended on, we have necessarily connected the broken materials in the 
best manner in our power. The great point we aim at in the Uralian Map, is to show 
a regular succession of the unaltered palaeozoic deposits (3, 2 and 1) on the west flank 
of the chain, until they reach the great fissure of eruption along which they have been 
crystallized and metamorphosed (c, e 1 , e 9 , c 8 ) ; whilst on the east flank of the chain, though 
much dismembered and insulated amidst a vast spread of various igneous rocks, the same 
palaeozoic masses are still recognisable, and occasionally become quite distinct when fol- 
lowed down into the low countries of Siberia (as on the river Issetz). 
Humboldt, Rose, Helmersen, Hofmann, Erman, Tchihatcheff, Middendorff and other ex- 
plorers of Siberia having, through the fossils brought back by them, satisfied us that the 
same rocks we define in the Ural, are largely developed in wild regions far to the east of 
these mountains, so we are led to hope, that the classification we have attempted may be 
of use in methodizing the arrangement and description of the chief Siberian rocks. 
Another object is to show at a glance, that although originally composed of sedimentary 
formations essentially the same, and all affected on the same great meridian strike, the 
mountains of the North and South Ural offer some remarkable features of difference. In 
the former, the ancient deposits to the west of the axis contain but little quartz rock, whilst 
in the broad south-western expansion of the South Ural, such rocks (c 1 ) abound, and con- 
stitute some of the loftiest ridges, including the Iremel. 
The gold alluvia, extending to the river Losva, and a little beyond the limits of the Uralian Map, 
( w ith the single exception of Chrestovodsvisgensk, near Bissersk, in parallel 58g°) are 
found on the eastern side of the great axis of mineralization. Taking Ekaterinburg as the 
centre of these auriferous deposits, they may be seen, as indicated by the bright gold 
colours dotted at intervals, to extend pretty nearly as far south as north of that city. They 
die away, however, in the parallel of Tanalysk; and to the south of the Lake Aushkul and 
Cossatchi-Datchi, few of the sites are worthy of much attention. This thinning out of 
the gold ore is accompanied by that remarkable change in the lithological features of the 
southernmost Ural, whereby schists of the carboniferous and other palaeozoic rocks are 
interlaced wdth countless ridges and bands of porphyry, in contact with which they are con- 
verted into the far-famed Siberian jaspers (c 8 ). By traversing the Irendyk Ridge, which 
forms the chief axis of the South Ural in the parallels of Verkny Uralsk and Kizilsk, and 
also by crossing the end of the chain at Orsk, we had abundant opportunities of con- 
vincing ourselves, that the siliceous and flinty schists and jaspers are simply metamorphosed 
palaeozoic strata (often carboniferous), which followed from north-north-west to south- 
south-east, terminate at Kizilsk, Urtazimsk and Tanalysk, in masses of carbonifei ous shale, 
the limestone associated with which is replete with Producti and Encrinites. 
