134 PROFESSOR JAMES GEIKIE ON THE 



morainic deposits that overlie the interglacial beds of Central Kussia cannot, therefore, 

 belong to the epoch of the great Baltic glacier. They are necessarily older. In short, 

 it is obvious that the upper and lower glacial accumulations near Moscow must be on the 

 horizon of the lower diluvium of North Germany. And if this be so, then it is clear that 

 the latter cannot be entirely the product of one and the same rner de glace. When the 

 several boulder-clays, described by Schroder and others as occurring in the Baltic pro- 

 vinces of Germany, are reinvestigated, they may prove to be the bottom-moraines of as 

 many distinct and separate glacial epochs. 



It may be contended that the glacial and interglacial deposits of Central Eussia are 

 perhaps only local developments — that their evidence may be accounted for by oscillations 

 of one single mer de glace. This explanation, as already pointed out, has been applied 

 to the boulder-clays and intercalated aqueous beds of the lower diluvium of North 

 Germany, and the prevalent character of the associated organic remains makes it appear 

 plausible. It is quite inapplicable, however, to the similar accumulations in Central 

 Russia. During the formation of the freshwater beds of Troizkoje, no part of Russia 

 could have been occupied by an ice-sheet ; the climate was more genial and less " con- 

 tinental " than the present. Yet that mild interglacial epoch was preceded and succeeded 

 by extremely Arctic conditions. It is impossible that such excessive changes could have 

 been confined to Central Russia. Germany, and indeed all Northern and North-Western 

 Europe, must have participated in the climatic revolutions. 



So far, then, as the evidence has been considered, we may conclude that three glacial 

 and two interglacial epochs at least have been established for Northern Europe. If this 

 be the case, then a similar succession ought to occur in our own islands ; and a little 

 consideration of the evidence already adduced will suffice to show that it does. It will 

 be remembered that the lower and upper boulder-clays of the British Islands are the 

 bottom-moraines of two separate and distinct ice-sheets, each of which in its time 

 coalesced on the floor of the North Sea with the inland ice of Scandinavia. It is obvious, 

 therefore, that our upper boulder-clay cannot be the equivalent of the upper diluvium of 

 the Baltic coast-lands, of Sweden, Denmark, and Schleswig-Holstein. De Geer and 

 others have shown that while the great Baltic glacier was accumulating the upper 

 diluvium of North Germany, &c, the inland ice of Norway calved its icebergs at the 

 mouths of the great fiords. Thus, during the so-called " second " glacial epoch of Scandi- 

 navian and German geologists, the Norwegian inland ice did not coalesce with any British 

 mer de glace. The true equivalent in this country of the upper diluvium is not our 

 upper boulder-clay, but the great valley-moraines of our mountain regions. It is our 

 epoch of large valley-glaciers which corresponds to that of the great Baltic ice-flow. Our 

 upper and lower boulder-clays are on the horizon of the lower diluvium of Germany and 

 the glacial deposits of Central Russia. 



It will now be seen that the evidence in Britain is fully borne out by what is known 

 of the glacial succession in the corresponding latitudes of the Continent. I had inferred 

 that our epoch of large valley-glaciers formed a distinct stage by itself, and was probably 



