364 SILURIAN, DEVONIAN AND CARBONIFEROUS ROCKS OF TFIE ISSETZ. 
rises in an arch from beneath these schists and grits, and as it contained the Tere- 
bratula reticularis, a shell never found in the carboniferous rocks, associated with 
casts of large Euomphali, we consider it to be Devonian. The courses of limestone 
and schist which extend to the mill of Tcherdinsk seemed to be repetitions, and we 
could not resist the impression, that the great masses of rapidly undulating lime- 
stone and schist near the village of Swagba, as well as certain black calcareous schists 
by which they are covered, were also of the true Devonian age, for they are covered 
by other limestones, schists and grits, which are clearly carboniferous. Whether the 
same neat division between the Devonian and Carboniferous limestones can be read 
off upon the Issetz, as that which we shall presently indicate upon the Tchussovaya 
on the west flank of the chain, must be determined by longer observation and a 
further discovery of fossils. Nor can we pretend to decide, whether the siliceous 
conglomerate and sandstone with some traces of coaly matter, which overlie the 
black schists and underlie the carboniferous limestone, ought to be grouped with 
the one or the other of these systems. For the present we must content ourselves 
with expressing our belief, drawn from the analogy of succession in other parts of 
the Ural, that the lower black schists and limestones on the Issetz are Devonian. 
Adopting this view from the order of superposition upon the river, we were the 
more disposed to adhere to it, when in subsequently extending our researches into 
the interior, we found other schists and sandstones, sometimes red and green, 
with coarse grits and conglomerates, flanked at Bagaratz by true carboniferous 
limestone containing large Producti. A tract like this, perforated at numerous 
points by porphyry, greenstone and other eruptive rocks, cannot be expected 
to offer a regular sequence of ascending or descending order of deposits ; the neces- 
sary result of such intrusion being, that in the numerous contortions and breaks 
to which the invaded strata have been subjected, they are often so bent back, 
that the older strata are placed above the younger, — a phsenomenon now so 
clearly pointed out in other disturbed countries, that it is unnecessary here to 
dwell upon it 1 . 
A few versts to the south of the Issetz, we found, indeed, distinct proofs that 
sedimentary strata, older than any we saw in the gorges of the Issetz, had been 
forced up into the adjacent plateau. On the banks of a little stagnant streamlet 
called the Istok, and at the villages of Crasnoi-glasnova and Gashin-novo, three 
or four versts asunder, a small dome of light-coloured, whitish-grey, crystalline 
1 See Silurian System, pp. 421, 423 et passim. 
