380 
SILURIAN ROCKS NORTH OF KUSHVINSK. 
mountain, contained similar iron ore. Now that we are acquainted with this fact, 
which so clearly demonstrates the magnetic iron ore to have been erupted 1 , we have 
no hesitation in agreeing with our skilful cotemporary, who has so closely studied 
the rocks of Blagodat, that these great masses of iron ore have flowed into this 
depression from fissures in the adjacent hill, and that they have since been cut 
through by other dykes of similar matter. In our description of the Katchkanar 
we shall adduce independent proof of the igneous origin of magnetic iron. 
Besides the porphyry and magnetic iron of the Great and Little Blagodat, the 
environs of Kushvinsk are surrounded by a vast number of other eruptive rocks 
differing in mineral composition, the outlines of which were laid down by the 
Russian mining engineers in a detailed map of the rocks around the Zavod, which 
had been prepared for our use. These intrusive rocks so predominate, that the 
original sedimentary strata are only to be detected in very small and isolated 
fragments, or in bands of highly altered chlorite schists. The important point, 
however, for geologists like ourselves to dwell upon was, that whether composed 
of hornblendic greenstone as at Nijny, or of greenstone porphyry as at Laisk 
and Blagodat, all the intrusive rocks on this zone are upon the same line of erup- 
tion, and all, according to our view, have produced varied metamorphic and mineral 
effects upon the stratified deposits. 
But still amid this chaos of eruptive and metamorphic rocks, well-known sedi- 
mentary strata are to be detected at intervals. Thus we observed fossiliferous 
limestones a little to the north of Ivushvinsk in a highly cultivated tract through 
which the road to Bogoslofsk passes 2 . To the west of that route, about fifteen 
versts south of Nijny Turinsk, in the midst of the forest, and on the banks of a 
rivulet known among the Russian settlers as “ Retchka Isveostka,” or limestone 
brook, we met with strong beds of limestone striking to the north-north-west, 
1 See M. Le Play’s confirmation of this view, ante, p. 376. 
8 In writing to us concerning the igneous origin of the magnetic iron ore, M. Le Play, after stating 
that Nijny Tagilsk and Blagodat are not the most appropriate localities for this inquiry, thus expresses 
himself : — “ La question se resout surtout par l’etude des roches crystallines, qui forment de si grandes 
masses, soit dans le centre de la chaine de l’Oural, soit dans les contrees qui s’etendent vers l’est, du cote 
de la grande steppe de Siberie. Le fer oxydule y est, pour ainsi dire, uu occupant constant des roches 
crystallines, il la maniere de Valbite et de Vamphibole ; et 9 a et la il y forme des montagnes oil le fer abonde 
plus que les autres elements : en beaucoup de points il forme des gites speciaux, ou les autres elements 
disparaissent presque completement, et qui sulfiraient seules a alimenter des lmuts fourneaux pendant des 
centaines d’annees .” — Extract from, a Letter to Mr. Murchison dated Ekaterinburg , August 30, 1844 
