ScHARFF — On the Origin of the European Fauna. 497 



mer de glace, which crept in upon the land from the north-east, and 

 brought the erratics ; and that the ice-sheet, which formed over Great 

 Britain, was kept back for a long time by this superior mass, which 

 flowed outwards from the Scandinavian peninsula, but that, as the 

 North Sea ice-flow diminished in bulk, the British ice, which formed 

 the purple clay, was enabled to reach the coast-lands. 



It seems to me that the theory of the marine origin of the boulder- 

 clay offers the following simpler explanation. After the Interglacial 

 phase of the Glacial Period had passed away, a renewed transgression 

 of the Arctic waters must have occurred, but the sea did not again 

 invade Central Russia. As Prof. J. Geikie has pointed out (35 a, 

 p. 463), the erratics included in the upper boulder-clay of Northern 

 Uontinental Europe have travelled in a different direction from those 

 contained in the lower. A change of current, therefore, evidently 

 took place, owing to the fact that the Northern European Sea was not 

 now connected with the Ponto-Caspian basin.' 



A large number of erratics would therefore be brought by Scandi- 

 navian icebergs stranding on the east coast of England, which was 

 gradually being submerged by the advancing marine transgression. 

 As the water rose, the local glaciers which had begun to form on the 

 mountains of the north of England and Scotland, cast off icebergs 

 which scattered detritus and boulders over the plain. 



On p. 366, in speaking of the upper boulder-clay of Holderness, 

 Professor J. Geikie refers to the reappearance of the great mer de 

 glace in the North Sea. He infers its presence from the fact that 

 many of the erratics which occur in the clay have been brought down 

 from the high grounds of England to the sea coast, and thereafter 

 have travelled southwards. " Obviously," he says, " the British ice 

 was unable to flow right out to sea ; its progress in that direction was 

 barred, and its course determined by the presence of another Scandi- 

 navian ice sheet." 



An interesting observation which might lead one to a similar con- 

 clusion was made by Mr. Kendall, from a study of the erratics in the 

 north of England (96, p 155). It would appear from this, that a portion 

 of the Solway glacier was pushed over the watershed into the valley 

 of tlie Tyue, that is to say, from the west coast of England to the 

 east coast. " The fate," he says, " of those elements of the Solway 

 glacier which reached the sea is not left entirely to conjecture." 



1 Tliis again is of great importance in establishing the contemporaneousness of 

 the upper Continental boulder-clay with the whole of the British clays. 



