588 Geological Society '. Anniversary Address, 184/2. 



sea shells of an arctic character, that the " terra firma " to which 

 some of the blocks had been transported, had been the bed of the 

 Northern or glacial Sea at the period of this transport. We then 

 attempted to explain how the parallel striae and polishing of the 

 surface of rocks of unequal altitudes was reconcileable with the 

 suhmarine action of ice, by supposing that ice floes and their de- 

 tritus miglit be set in motion by the elevation of the Scandinavian 

 continent, and the consequent breaking up of great glaciers on the 

 northern shores of a sea whicli then covered all the flat regions of 

 Russia ; and we further stated our belief, that the bottoms of these 

 icebei'gs, extending to great depths, must have every here and there 

 stranded upon the highest and most uneven points of the bottom 

 of the sea into which they floated ; that where the bottom was hard 

 rock, the lower surface of the iceberg, like the lower surface of a 

 glacier, would grate along and score and polish the subjacent mass ; 

 that where the bottom consisted of tenacious mud or clay, the ice- 

 berg once fairly sti'anded would be retained till it melted away, 

 entirely or in part, whilst it would be more frequently borne over 

 sand-banks, on account of their less resistance. In this manner, we 

 endeavoured to explain not only the scratches and polish of hard 

 submarine rocks, but also why large blocks are often found on former 

 submarine hills, and why (in Russia at least) such blocks are more 

 frequently associated with clay than sand. These views were indeed 

 first expressed at the Glasgow meeting of the British Association, 

 when I strove to i-educe a large portion of the Alpine glacial theory 

 to considerations depending upon the fact, that during the aera of 

 the dispersion of the large blocks, by far the greater portion of our 

 continents were beneath the sea. 



Mr. Maclaren, to whom I have already adverted, has recently im- 

 proved this view, by showing how the parallel scratches and grooves 

 ranging from N.N.W. to S.S.E., and the dispersion of blocks in that 

 direction, ai-e reconcileable with the union of currents from the N., 

 set in action, as above supposed, by a great polar elevation which 

 acted as a " centre of dispersion ;" but, as this author adds, a broad 

 current would also set continually eastivard along the immersed re- 

 gions included in the temperate zone ; and hence, he says, that when 

 the icebergs were drifting southwards from the poles, they would na- 

 turally be carried to the S.E. by a stream compounded of the two 

 currents. After reasoning upon the wide application to which the 

 view of floating iceberg action is capable, and how many of our pre- 

 sent terrestrial appearances it will explain, Mr. Maclaren adds, " Mr. 

 Murchison's hypothesis, if adopted, does not exclude that of Agassiz. 

 On the contrary, it may be assumed, that while the glacial condition 

 (which caused the great accumulation of ice in the northern re- 

 gions) continued, every mountain chain, which thoi had an eleva- 

 tion of 2000 or 3000 feet above the sea, would be encrusted with 

 ice, perhaps as far south as the latitude of 40°. Each of these would 

 be on a small scale what the polar nucleus was on a great scale, a 

 centre of dispersion." 



In the memoir upon Russia by M. de Verneuil and myself, one 



