GYPSIFEROUS ROCKS OF THE DWINA. 
173 
with courses of limestone. In the latter we sought diligently for fossils, notwith- 
standing torrents of rain and the persecution of myriads of mosquitoes, whose 
numbers seemed to be greater than the drops of water in the storm 1 . The thickest 
course of dividing limestone at this spot never exceeds two or three feet, and 
the rock is very fissile, marly, and void of fossils. On the banks of the river above 
Pinega, the cliff 2 is composed in ascending order of — 1. Ten to twelve feet of thin- 
bedded limestone, the bottom beds of which are charged with Turritellse, Aviculse, 
Turbo, and other forms dissimilar from carboniferous fossils. 2. Gypsum, with 
some thin courses of marly limestone. 3. Band of limestone two or three feet 
thick. 4. White gypsum. 5. Red crystalline gypsum. 6. Red and argillaceous 
sandstone, with small intermixed concretions of gypsum. 
In a word, the banks of the Pinega clearly showed (all the strata being hori- 
zontal), that the carboniferous limestone was overlaid by the gypsiferous or lower 
bands of the Permian system. 
Ascent of the Dwina. — Limestone with Gypsum, Marls and Sands. — Limestone 
with Fossils of the Zechstein. — Overlying Sands, Marls and Tufaceous Limestones . — 
In ascending the Dwina, from the same base of carboniferous limestone to which 
allusion has just been made, and after travelling over much sand and detritus, we fell 
in with cliffs of gypsum and thin courses of limestone, exactly similar to those of 
the Pinega. These first begin to show themselves on the left bank, at about three 
versts north of the post-station of Zaborskaya, where the gypsum is both red and 
white. First ranging on the level of the river, these bands rise gradually to about 
fifteen versts from Kaletzkaya, where they form cliffs from forty to fifty feet high. 
The red courses then disappear, and the whole being pure white, the effect upon the 
eye is that of a continuous band of snow or ice, surmounted by a dark green line 
of fir-trees, as seen on both banks of a noble river, two-thirds of an English mile 
in width, and for a distance of more than twenty versts. In a word, the Dwina 
here runs in a long gorge of alabaster. 
This gypsum is then clearly subordinate to the Permian system, being precisely 
1 The case containing these fossils was unfortunately lost. We may here observe, that mosquitoes 
constitute the chief impediment to geological research during the hot summer months, in all these high 
latitudes, and particularly where wood and water abound. The hardy natives even are compelled to work 
in cowls, like those of Capucin friars, through which their eyes, nose and mouth only are seen ; and we 
were driven to the use of masks and veils. 
2 In this cliff a large cavern exists, used by the peasants for cellarage and said to be two versts 
long. 
