DIRECTION OF THE URALIAN ROCKS. 
467 
the South Ural, on the contrary, the great radiating western branches trend from 
north-north-east to south-south-west; and whilst the chief axis in the Irendyk, with 
numerous masses on the west of the Sakmara and in the line of the Ural river, holds 
its course to the south, many of the rocks which flank it on the east, resume the 
prevalent strike of the strata in the North Ural, and trend from north-north -west to 
south-south-east. Seeing that the interstratified and contemporaneous igneous 
rocks Avhich appear at the Katchkanar and other places along the crest of the 
chain, have the same direction as the adjacent sedimentary masses, we believe that 
the meridian alinement of the ridge began to be impressed upon it at the very 
earliest period when the original sediments were formed ; in other words, that 
from the most primaeval traceable period, there has been a fissure more or less de- 
vious from the meridian, by which igneous matter has been extravasated at different 
periods. If our own observations were not adequate to establish this point, our 
readers may draw the same conclusions from the writings of Baron Humboldt, 
as well as from the details of Mr. G. Rose, in his description of certain stratified 
masses which lie between Nijny Tagilsk and the crest of the chain 1 . Humboldt, 
Rose, Helmersen and Le Play, all, indeed, concur in showing the prevalence of the 
latter rock along this crest of the Ural, and even upon its western side, where it is 
succeeded by black dolomites, occasionally fossil iferous, associated with chlorite 
and talc schists. 
There were, then, we conceive, plutonic evolutions of slaty hornblende rock 
during the earlier portion of the Silurian period all along this great fissure, and 
these, after periods of repose, were followed by outbursts of greenstone, porphyry 
and other eruptive rocks. The effects produced during one of these periods ol 
disturbance, are partially seen in a few conglomerates of the Old Red Sandstone or 
Devonian age, as well as in the fragmentary and altered condition of the Uppei 
Silurian limestones along the eastern flank of the chain. Again, an agitation of 
this chain is distinctly marked by the coarse conglomerates at the close of the car- 
boniferous age, which from the very nature of their materials, must at one time 
have been deposited in shallow water and positions more or less horizontal. In 
such positions, indeed, they are still found, when remote from the eruptive axis ; 
but on approaching that line of igneous disturbance, these very beds (in one portion 
of the mountains) are thrown upon their edges, in the manner which we have 
1 M. Rose has there described two long linear masses, the one of limestone in a highly granular state, 
the other of conformably interstratified hornblende slate. 
