CARBONIFEROUS LIMESTONE, ETC. 
409 
again prevail, when they alternate with fragile, argillaceous schists and grey quaitz 
rock, all of which are in highly inclined or sub-vertical positions. On the left 
bank of the stream, brown and brittle argillaceous schists constitute a mountain 
called Pulnaya-Gora, or Ball Mountain, so called because it is charged with many 
argillo-ferruginous concretions of a perfectly spherical form, another Silurian ana- 
logy, well known to all geologists who have examined the gorge of the Severn 
above Madeley, or the hanks of the Banw in North Wales. The quartzose schists 
terminate in ascending order, with an inclination of 20° towards the west or lower 
country. 
Carboniferous Rocks .—' The Silurian masses above described are directly suc- 
ceeded, and without any apparent unconformity, by carboniferous strata; thus 
showing, that in this part of the Ural, at all events, no portion of the Devonian 
group exists (see Map and Section, PI. V. fig. 3). Unable to trace any great fault, 
or any decisive unconformability along this line, we are disposed to think, that the 
highly incurvated basin into which the Silurian rocks are here thrown, was formed 
before the Carboniferous beds began to accumulate, and that the upraised strata 
were placed beyond the influence of those waters under which the true Devonian 
beds were deposited. 
The base of the carboniferous rocks, formed of thick beds of dark compact 
limestone, containing concretions of chalcedonic chert, and alternating with black 
shale, constitutes a sub-formation very much resembling the lower mountain 
limestone of Northumberland, Yorkshire, the Isle of Man, and the lower slaty 
group of Ireland. 
The characteristic fossils of these lowest beds are, Spirifer expansus, Phil, (lam- 
gat a, var.), Orthis arachnoidea (Phil.), Clxonetes fornicatus, n.s., with Caryophyllia 
and Cyathophyllum ; whilst in the strata which immediately succeed to them is the 
Productus hemisphcericus, Sow. (var. minor.) 
This carboniferous limestone is powerfully developed on the banks of the Iletsk, 
and occupies heights of 500 feet above its bed, as far westwards as the gorge called 
Stone-gate, where the rock is exposed in vertical cliffs of about 200 feet in height, 
through which the river escapes. The stratification of these limestones is often 
obscure, and is chiefly recognizable by lines of corals ; the beds are powerfully 
bent both to the east and west, and the strike is persistent from north to south. 
The chief lithological character (that of the mountain limestone of many parts 
of England) is undistinguishable from what we have described in the previous 
