332 
RAISED SEA BOTTOMS OF THE PETCHORA. 
in Norway and America occur at various levels from 40 to 600 feet 1 . Now as we 
necessarily infer, that waters containing identical oceanic species must have stood 
at the same level, and cannot have lain at such different heights within the same 
recent period, no reasonable hypothesis can be entertained, except that to which we 
have alluded in speaking of the former Caspian deposits, and which refers these 
different, levels of the same sea-beds to different degrees of elevation. It is, indeed, 
almost unnecessary, in the present state of geological science, to sustain by our 
northern examples, that which has been so clearly demonstrated around the coasts 
of the British Isles and North America, and of which such decisive proofs have 
been already adduced in this work from the South of Russia. 
The nature and origin of the superficial detritus which covers these Arctic shells 
will be hereafter explained ; but we may here, however, remark, that the coarse 
gravel and sand, which surmount the beds of shells upon the Vaga and the Dwina, 
and which we cannot well separate from the erratic block phtenomenon, must all 
have been accumulated under water. 
We may now say a few words upon the nature of the other recent marine deposits 
in the north-east of Russia, to which allusion has previously been made, though we 
are not yet furnished with full details. Fragments of sea-shells, apparently of ex- 
isting Arctic forms, have been observed by Count Keyserling (1843) in many parts 
of the valley of the Petchora, extending inland to upwards of 3° of latitude south 
of the mouth of that river (68 J to 65^ north latitude), on the banks of which 
they are strewed about upon argillaceous slopes, for the most part composed of 
Jurassic shale. They do not, however, show themselves in regular beds, like those 
of the Dwina or the Yaga. 
This observation of our friend is valuable in enabling us to form a more correct 
opinion now than during our first tour, respecting the relations of some of these 
sea-bottoms to other superficial detritus. He has remarked, that the shells are 
found in the depression of the great valley of the Petchora only, and never on the 
plateaux, nor even in the tributaries of that river which descend from and cut 
through such plateaux, and hence he believes, that such shelly deposits were 
formed in an estuary of the northern ocean, which penetrated into a continent 
that had already, to a great extent, assumed its present contour. In fact, we 
1 For more details upon the subject of the elevation of the coasts of Norway, we recommend our 
readers to peruse the highly instructive memoir of M. Elie de Beaumont, entitled “ Rapport sur un Me- 
moire de M. Bravais” (Extrait des Comptes Rendus a l’Acad. des Sciences, 31 Oct. 1842). 
