748 
extent by all the parallel ridges which flank it on the eastern or 
Siberian side. 
The Ural-tau or crest is to a very great extent a wall of schist 
and quartz rock diversified by points of igneous rocks, and though 
of no great altitude, it is very remarkable that throughout 17 de- 
grees of latitude this water-shed is not broken through by any great 
transverse valley. The Ural-tau marks, in fact, one long line or 
fissure of eruption. With the exception of the gold mines near 
Bissersk, on its west flank, all the gold alluvia of the chain occur 
on its eastern flank ; and when it is stated that this circumstance is 
connected with the fact, that all the great masses of igneous rocks 
have been evolved on the eastern flank, it will at once be seen (as 
insisted upon so well by Humboldt) that there is an intimate con- 
nexion between the eruption of plutonic rocks and the formation of 
the gold mines whence the local alluvia have been derived. That 
this connexion exists in regard to other mineral veins, is also 
equally apparent in the Ural mountains ; for with very rare excep- 
tions, it is only on their eastern or eruptive side that copper veins, 
malachite, platinum and magnetic iron prevail*. 
Without entering into all the lithological distinctions of the North 
Ural, they advert specially to the occurrence in the districts of 
- Turinsk and Nijny Tagilsk of a stratified and regularly bedded por- 
phyry, which they compare with the ‘‘ Schaalstein”’ of German geo- 
logists, and which on the banks of the Kakwa and east of Bogos- 
lofsk}, as in the Rhenish provinces, alternates with limestone strata 
of Devonian age. In the copper mines cf Turyinsk, the veins and 
masses of ore are shown to be intimately connected with the intrusion 
of greenstone, between a thick mass of which and the metalliferous 
veins is a garnet rock. This phenomenon is a counterpart to that 
formerly described by Professor Henslow in the Isle of Anglesea ; 
whilst on the river Kakwa, the ordinary limestone (Devonian?) has 
been converted by a dyke of greenstone into white granular marble, 
in the same way as by the contact of syenite the lias limestone of 
the Isle of Sky has been changed. - 
The Katch-kanar mountain (lat. 58° 44’), which the authors vi- 
sited by a little-frequented pass, is composed of augitic greenstone 
and magnetic iron, the latter in so hard and crystalline'a state that 
it is not worthy of extraction and manufacture. The most pro- 
ductive masses of magnetic iron are at the Government establish- 
ment of Mount Blagodat, and that of Nijny Tagilsk, belonging to 
M. Anatole Demidoff. In both these cases the ordinary varieties of 
iron occur in great masses, occasionally with chromate of iron{, in 
* In sketching the chief relations of the plutonic and metamorphic rocks 
of the North Ural, much praise is given to a detailed geological map of the 
environs of Bogoslofsk by Capt. Karpinski, of the School of Mines, with a 
copy of which the authors were furnished. 
+ See Geol. Trans. vol. vi. pp. 246, 248. 
+ The largest masses of chromate of iron occur in the South Ural, near 
the mines of Polikofski, south of Miask, and from whence from 6000 to 7000 
““ nouds”’ per annum have recently been sent to Moscow. 
