122 K. KEILHACK 



glacial periods there is a satisfactory conformity between the ice 

 expansions of Great Britain and those of north Europe and the 

 Alps, such conformity is altogether wanting in Geikie's assumed 

 fourth epoch. The Baltic glacier supposed by him to belong to 

 the fourth period is still of such immense size, and is so little 

 inferior to those of the earlier epochs, that it is almost impossible 

 to correlate it with the valley glaciers of the Alps which Penck 

 has described, and it seems to me with perfect right, as repre- 

 senting only postglacial episodes. Hensen has regarded the 

 similar deposits of Norway as epiglacial projections of existing 

 glaciers. A graphic representation, such as that of Fig. i shows 

 better than words can, the unnaturalness of Geikie's classification. 

 If we suppose the expansion of the north European and Alpine 

 glaciations to be expressed by lines which represent the extent 

 of glaciation from the northern end of the Gulf of Bothnia, and 

 from the central Alps respectively, and if the lines which repre- 

 sent the greatest extremity of ice be represented by unity in 

 both cases, we obtain the proportions expressed by the follow- 

 ing figures : 



Alps, scale i : 3,400,000. 



North Europe, scale i : 23,500,000. 



I- I— 

 11. I— 



III. ! — 



IV, I— 



I. I 1 



II. I — — I 



ni. I —1 



IV. I 1 



If, however, one considers the Baltic terminal moraine as 

 well as all others which lie further south, only as stages in the 

 retreat of a single ice-sheet, as the Prussian Geological Survey 

 has done, and so unites Geikie's No. 3 and No. 4 into No. 3, all 

 difficulties of comparison at once disappear, i, 2 and 3, in north 



