320 Horner's Geological Address. 



profusely spread over their southern slopes. In the sandy 

 plains east of Posen, not a block is to be seen for several miles, 

 until the elevations towards the Polish frontier are reached, 

 and they again become numerous. In the sandy plain the 

 blocks are usually small, but on the hills between Konin and 

 Kolo, vast numbers of large blocks are buried in and mixed 

 with sand, at heights of 300 or 400 feet above the sea. 



A very important circumstance in the history of these erra- 

 tic blocks is pointed out by the authors of the " Geology of 

 Russia," viz., that they have not travelled from north to south 

 only, but in all directions from certain centres in Scandinavia 

 and Lapland. In Denmark they have come from north by 

 east ; in most parts of Prussia almost direct from north ; op- 

 posite the coasts of Finnish Lapland, where the granitic and 

 other crystalline boundary sweeps round to the north-east, the 

 direction of the blocks changes accordingly. Near Nijni No- 

 vogorod they must have travelled from north-west to south 

 east ; and in the Government of Vologda they have nearly an 

 eastern course. By the observations of Bohtlingk, we learn 

 that the erratic blocks of Scandinavia have been shed off from 

 the coast of Kemi into the Bay of Onega, and from Russian 

 Lapland into the Icy Sea, in north-eastern, northern, and north- 

 western directions ; and Norwegian detritus has been trans- 

 ported westward to the coasts of Norfolk and Yorkshire. 



Russia in Europe, from the nature of its surface, cannot be 

 supposed to afford many proofs of furrows, grooves, and striae, 

 on hard rocks ; but on Lake Onega a hard greenstone and 

 siliceous breccia are rounded off, grooved, and striated, on the 

 northern face of a small promontory, the direction of the 

 grooves and striae being north and south, and the striae are to 

 be seen, through the transparency of the water, eight feet be- 

 low its surface ; they are also to be traced near the summit of 

 a low hill. On the south side of that hill, however, no such 

 traces of wearing or friction can be seen, " and thus," the au- 

 thors say, " we had before us, on the edges of Russian Lap- 

 land, the very phenomenon so extensively observed by Sefstrom 

 over Sweden, viz., a rounded, worn, and striated surface of the 

 northern sides of promontories, whose southern faces are na- 

 tural and unaffected by any mechanical agency." 



