Vol. 52.] PLIOCENE DEPOSITS OF HOLLAND. 775 



Pleistocene deposits of Utrecht and Amsterdam being composed 

 of stratified gravels and sands. It is difficult, therefore, to see how 

 the Baltic glacier could have reached East Anglia, though ice-floes 

 with Scandinavian boulders might easily have done so, while had the 

 Norwegian ice filled the North Sea and overflowed the county of 

 Norfolk, some evidence of its presence ought to be found in the 

 Glacial beds of Holland. 



The great thickness of the Amstelien as compared with the 

 Scaldisien strata is perhaps worthy of notice, but whether it may be 

 taken as an indication of the comparative duration of these periods, 

 or only of the comparative amount of sediment brought down by the 

 rivers draining into the Pliocene sea, cannot be decided. 



Some of the shells found in the Amstelien beds are not merely 

 British species with a northern range, but boreal forms, which are 

 not now found beyond the limits of the Arctic Circle. The climate 

 of Northern Europe was at that time considerably colder than it is 

 at present, and the glaciers of the mountain districts drained by the 

 Rhine were on a larger scale, with probably a corresponding increase 

 of the sediment brought down by it. 1 



When we attempt to restore in imagination the physical conditions 

 of the Pliocene era in Northern Europe, three features stand out 

 with a certain amount of distinctness : the river Rhine, the basin of 

 the North Sea, and the gradual refrigeration of climate which from 

 the earliest times of the Upper Crag seemed to be heralding the 

 approach of the Glacial epoch. 



It has often been said that Holland is the ancient delta of the 

 Rhine, but these borings show that the formation of this delta had 

 commenced as early as the Diestien epoch. During the whole of the 

 Pliocene period, and indeed up to the present day, the rivers of 

 Northern Europe have continued to pour down their sediment, 

 heaping it up on the gradually subsiding bottom of the North Sea. 

 The North Sea basin also, bounded in the first instance on the east 

 by the Miocene deposits of Germany, on the south and west by the 

 older Tertiary and Cretaceous rocks of Belgium and East Anglia, 

 had equally come into existence before the deposition of the Coralline 

 Crag. Since then it has been affected by the great movements of 

 subsidence and elevation which took place during the Glacial and 

 post-Glacial periods. As to the changes of level which occurred 

 during the former, geologists are by no means agreed, but these 

 must have affected the area in question, while in the pose-Glacial 

 era the North Sea basin formed at one time a great plain, tenanted 

 by herds of elephants, whose bones and teeth are still dredged by 

 Yarmouth fishermen. During the deposition of the Upper Crag 



1 Swiss geologists maintain that the glaciation of their country commenced in 

 Pliocene times, and that milder conditions of climate intervened between it and 

 the subsequent advance of the ice during the Pleistocene era. See Dr. Preller's 

 paper in Quart. Journ. Greol. Soc. vol. li. (1895) p. 369 ; also Dr. A. BZeim, 

 1 Die Geologie der Umgebung von Zurich ' (VI. Internat. Geol. Congr. 1894), 

 p. 181. If this was so, this interglacial period may possibly have coincided 

 with the deposition of the earlier portion of the Cromer Beds, which, as we 

 have seen, indicate a climate somewhat milder than that of the Upper Crag. 



