328 
RAISED SEA-BOTTOMS OF THE YAGA. 
regularly imbedded in clay and sand of about ten feet in thickness, which, covered 
by about twenty feet of the coarse gravel and detritus of the country, reposed at 
once on bands of red and white gypsum, subordinate to red marls, which form a 
part of the rocks we have called Permian. The annexed woodcut conveys an idea 
of this order. 
49. 
We afterwards found similar beds on the right bank of the Vaga two stations 
further to the south. At the latter they rest on strata of the Permian limestone 
which we have before described, p. 174. As both these localities were seen to 
be in the valley of the Dwina or in one of its indentations, we had not at that 
time (1840) an opportunity of ascertaining, whether these shelly deposits extended 
continuously to any distance east and west ; but our colleague, Count Keyserling, 
having retraversed the tract during the summer of 1843, has discovered, that in the 
sections on the river banks of the upper portion of the Vaga, such shelly beds 
are not visible. We might, therefore, view them as relics of the sea, when the 
present embouchure of the Dwina was a bay or estuary which entered for upwards 
of 250 versts southwards into the adjacent low lands. At the same time it is ne- 
cessary to remember, that these shelly beds are covered by sand and gravel, which 
we should have great difficulty in separating from the superficial northern drift. 
A recent excursion through Sweden has, indeed, convinced us, that in the neigh- 
bourhood of Upsala, marine post-pliocene deposits containing the Tellina Bal- 
tica, are there covered by coarse gravel and large erratic blocks, as stated by 
Mr. Lyell 1 . 
Some of the shells on the banks of the Dwina and Vaga, which have been pre- 
served in the blue clay or marine mud, and thereby totally excluded from atmo- 
spheric influence, have retained all the freshness of their original colour, with their 
1 See Phil. Trans. 1835, Part I. 
