8 GEOLOGICAL MEMOIRS.
tinuation of those which form the coast. The peninsula is, besides,
contoured by a flat shore of sand of small extent, succeeded by mud,
which becomes very calcareous at great depths.
In the North Sea, as well as in the glacial ocean, submarine rocks border the fiords and the archipelagos of Norway and Lapland. Very extensive zones of clay extend along one part of Norway, and must doubtless be attributed to the cropping out of palaeozoic schists. Besides, as is usual, the ocean adjoining the peninsula of Scandinavia essentially exhibits a bed of sand ; mud reappears again, especially in the neighbourhood of argillaceous rocks, and in that case may probably be derived from their destruction.
The White Sea also exhibits an inland sea, connected by a wide strait with the glacial ocean. The most striking feature of its orography is a depth very much greater in its north-eastern portion and in the Gulf of Kandalaks than in its centre and the part nearest the ocean. The long Gulfs of the Dwina and of Kandalaks are placed the one upon the line of the other, and correspond with an important submarine depression, which is very strongly marked and parallel with the Dwina, as also with the principal rivers of these regions.
Soundings have shown the presence of rocks near the shores of the White Sea, particularly at its opening in the Gulf of Mezen, and also in the Gulf of Onega : these rocks even indicate a connexion of the peninsula of Lapland with the continent.
Sand covers vast surfaces at the entrance of the glacial ocean, but in the White Sea it only borders the shores, and silt or mud almost entirely covers over the bed. The extent of silt is doubtless due to the circumstance that the White Sea, by reason of its orography, plays the part of a settling-basin to the troubled waters that it receives in great abundance, especially at the time of melting of the snows ; it is also attributable to the fact that the ice which covers it during one portion of the year also contributes to facilitate the deposition of the silt. Shell-bearing beds are very limited in the White Sea, probably on account of the fresh and muddy waters which pour into it ; they, however, occur abundantly on the sands at the entrance to the glacial ocean. Hence it is to be seen that the mollusca multiply and also attain great development in very northern latitudes, and as far as within the Polar circle.
A study of the inland seas of the Old World reveals general and very striking characters both in their orography and lithology. First, their depth northwards is slight, and increases towards the south ; besides, the principal rivers empty themselves more especially on their northern sides. These features occur markedly in the Caspian Sea, the Persian Gulf, the Sea of Azof, the Black Sea, the Baltic, the Adriatic, and finally in the Mediterranean.
The Baltic, the Caspian, and the Adriatic present striking analogies ; for all three are less salt than the ocean : they receive a multitude of rivers and of streams, which transport a quantity of debris and tend to fill their basins ; they are especially remarkable by the great extent of their sandy deposits.
