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opinion, namely, the direction of motion of tiiat part of the ice-slieet 

 which reached our country. 



From an examination of sedimentai'j-rock erratics from tlie Gro- 

 ningen part of the Hondsrng, the results of wiiich he stated in his 

 dissertation, which appeared last year, Dr. Jonker came to the same 

 conclusion as Schroeder van der Kolk had arrived at from the 

 examination of igneons-rock erratics, especially from tlie Eastern 

 parts of tlie country, and as others too, namely "that the glacial 

 flow which has produced the glacial diluvium in the North of the 

 Netherlands was a Baltic one." He even thinks it possible to trace exactly 

 the course taken by the glacial flow which "has created the Groningen - 

 diluvium". To these statements I have to make serious objections. 



For long years, neglecting the available direct means of tracing 

 the direction of the glacial flow, such as the examination in situ of 

 the Qitetsdisteine — a study already recommended fourteen years 

 ago by our ev^er-lamented Schroeder van der Kolk — it has been 

 a custom in the Netherlands to be guided, in the determination of 

 the direction of the glacial flow, exclusively by the solid rocks from 

 which the stones carried towards ns by the ice were derived. It 

 was not taken into account, and indeed was not at all known in 

 former time, that the great Ice Age, during which the Northern 

 Diluvium of our country was deposited, was preceded by another 

 glacial epoch, of lesser importance, it is true, for the Northern ice- 

 sheet did not reach our countrj- then, but which was notwithstanding 

 the first real glacial epoch, by which the Pleistocene period was 

 introduced. In that first glacial epoch, the Scanian Epoch of Prof. 

 James Geikie, there lived in the North Sea the arctic fauna of the 

 Weybourn Crag, and, during the melting period of the Alpine ice, 

 our country received the Rhenish Diluvium. 



In that same epoch, in Scandinavia and in the uplands to the 

 East of the Baltic, on the plateau called Fennoscandia, an ice-sheet 

 was formed which, following the slope of the land, terminated in 

 the North Sea as drift ice, and, on the other side, descended into the 

 basin of the Baltic, as the first Baltic glacier. It is well known that 

 the sculpture of the Scandinavian peninsula and of Finland has 

 been accomplished almost entirely during the Tertiary period, at a time of 

 a much higher level of those countries. The ice, which afterwards repeat- 

 edly passed over these parts, removed principally only the loose 

 material, smoothing the surface. Thus the first ice-sheet found all 

 the superficial deposits, accumulated on the rocky land-surface in the 

 preceding long period of ei-osion, both on that highland and in the 

 basin of the Baltic with its other environments. 



