496 Geological Society. 



that the great masses of superficial detritus, whether clays, sands or 

 blocks, which cover so very large an area of the northern region, 

 were all referable to one epoch (diluvian) in which the bones of 

 great extinct quadrupeds were also imbedded. The duration of their 

 journey was not sufficient to enable the authors to make many di- 

 stinctions of age between these different masses ; but they have 

 commenced this division by the discovery of beds of clay and sand 

 on the banks of the Dwina and Vaga, upwards of 200 miles south 

 of the White Sea, which contain twenty-two species of shells, many 

 of which still preserve their colours, and which, having been referred 

 to Dr. Beck, of Copenhagen, have been pronounced by him to be all 

 of modern northern species. Mr. Lyell states that they are identi- 

 cal with the Uddevalla group described by him in Sweden. Mr. 

 Smith adds, that these shells are nearly all the same as those which 

 he has found in various ancient elevated sea bottoms around the 

 coasts of Scotland. In referring twenty of these to modern arctic 

 species, Mr. G. Sowerby doubts if a certain Mya has ever been found 

 recent, and states that a Cardium, approaching to C. ciliatum, is dif- 

 ferent from any northern form he is acquainted with, and near to 

 certain Australian types. This discovery, in which they were assisted 

 by Count Keyserling, who accompanied the authors in their tour to 

 Archangel, is conceived to be of high geological interest, as it de- 

 monstrates that, during the quasi modern period, the whole of the 

 vast flat country of north-eastern Russia was beneath the sea for a 

 considerable time, the eastern boundary of that sea being probably 

 the slopes of the Ural Mountains. 



Drift and Erratic Blocks. — Overspreading all the formations, and 

 greatly obscuring them, is a vast mass of detritus, the large granitic 

 and other crystalline blocks of which have excited much attention, 

 from the days of Pallas to the present time. This detritus, the blocks 

 of which have all been derived from the north, is shown to have 

 been deposited under the sea, or in other words, upon a sea bottom, 

 since it covers the above-mentioned shells. 



Notwithstanding the obscuration occasioned by this wide-spread- 

 ing drift, it is stated that the nature of the subsoil, or fundamental 

 deposits, can often be surmised from the colour of the superficial 

 clay and sand, and the materials of small detritus, the surface of the 

 Silurian zone being grey, that of the old red, red ; whilst the cover 

 of the carboniferous limestone is often charged with many broken 

 flints derived from the underlying beds of that formation, some of the 

 siliceous fragments of which have been transported further south- 

 wards, and spread over the regions occupied by the newer red and 

 oolitic deposits. Thus, as all the larger and harder blocks can be 

 shown to have been carried from the mountains on the N.N.W., so 

 in passing to the S.S.E. the finer ingredients, or matrix of the de- 

 tritus, is found to change by the successive additions of materials 

 derived from the denudation of the different members of the palae- 

 ozoic series. There is no instance of any substance having been 

 transported from S. to N., except by the modern action of streams, 

 and by local causes dependent on the present configuration of the 



