180 NIJNI NOVOGOROD — BANKS OF THE VOLGA, OKA AND KLIASMA. 
pierced to a depth of upwards of 400 feet. At Nijni Novogorod, where the Oka 
unites with the Volga, the right banks of both rivers offer splendid sections, in cliffs 
from 300 to 400 feet in height, of finely ribboned, red and green marls, with sub- 
ordinate courses of soft gritty flagstone, and soft yellowish sandstone, almost in the 
state of incoherent sand. The magnificent new roads which descend from the 
Kremlin to the lower town or fair, and the formation of the grand esplanade over- 
looking the Volga, have admirably laid open the strata. But notwithstanding these 
advantages, rarely to be met with in Russia, we were not able, after an assiduous 
search, to observe any organic remains, except a very minute bone, probably 
belonging to a fossil fish. The extraordinary subsidences to which these incoherent 
cliffs are subject, and the deep transverse furrows ( avrachs ) which cut through 
the table lands, give the fullest insight into the mineral characters of these rocks. 
Sections of Red Marls and Sands on the Volga below Nijni, and on the Oka and 
ICliasma Rivers. — The sections of Kazan, Sviask and the Dwina (see woodcut, 
p 152), having proved that limestones with the Zechstein fossils subside under a 
group of marls, with courses of tufaceous and impure limestone, precisely similar 
to those of the governments of Vologda and Kostroma, we have now simply to 
state, that all these masses are confluent, and that they spread over the central part 
of this red region. They occupy, in fact, the whole of the high lands on the 
right bank of the Volga between Kazan and Nijni Novogorod, and are traceable 
still higher up that river as stated, nearly to the city Kostroma. In ascending 
the Oka, the great tributary of the Volga, the same rocks are quite as largely 
developed to the parallel of the town of Gorbktof ; and on the right bank of the 
river we find them ranging as far as Viasniki, beyond which they are lost upon 
the west, under heaps of detrital matter which obscure their junction with the 
inferior deposit of carboniferous limestone. These marls, sands and tufaceous 
limestone are obscured, as before stated, by the same detritus, all along the eastern 
limits of the great carboniferous region of the Northern Governments. 
Let us first simply describe the features of such rocks on the Lowei \ olga above 
Kazan and on the banks of the Oka and Kliasma. Between Sviask and Tchebok- 
sar on the Volga, two and more courses of the tufaceous limestone, from twelve 
to fifteen feet each in thickness, and beds of two to three feet, are subordinate to 
ribboned and spotted marls, exactly similar to those desciibed on the Suchona. 
One of these limestones differs only from the other, in being a little darker and 
more compact; for both are essentially what would be called tufaceous. Ihe 
