436 OSBORN AND REEDS PREHISTORY OF MAN IN EUROPE 



Thus the British theory of deep submergence in Second Interglacial 

 times has been abandoned. 



[= III Glaciation, Polonian of Geikie] (Polonian = IV Glaciation 



by Leverett) 



After the temperate phase [= Second Interglacial] the Polonian- 

 Rissian glaciation advances anew over the British Isles, but less to the 

 south than the preceding Saxonian. In Ireland and Wales the advance 

 of the two glaciers was not very different, or at least their limits have 

 not been sharply traced, but in the center and the east of England the 

 limit of the "recent Drift" marks a sinuous line which lies a long dis- 

 tance north of the limit of the "old Drift"; the "upper Boulder-clay" of 

 Glaciation III (Polonian), strewn with moraines and drumlins, is in 

 striking topographic contrast with the monotonous surfaces of the "lower 

 Boulder-clay," leveled and cut by deep valleys. The deposits of this 

 glaciation are the "internal moraines," the "recent Drift," the "upper 

 Till," the "upper Boulder-clay." 



The Polonian glacier receded again to Scandinavia, leaving the country 

 bare and admitting the North Sea again to the British coast. In Scotland 

 the marine terrace of 100 feet, with an extreme arctic fauna (Peel en. 

 groenlandicus, Yoldia arctica, Tellina myopsis), is superposed on the 

 "upper Till" of Glaciation III (Polonian). This is attributed [rightly] 

 to a local isostatic elevation due to melting during Glaciation III 

 (Polonian) . They are considered by Leverett the correlatives of moraines 

 of the last or fourth glaciation in Germany, outside of Geikie's Mecklen- 

 burgian. [Leverett (1901.1) examined moraines in Vale of York and 

 elsewhere in northern England which are here classed as Polonian, and 

 they now seem to him too fresh to be so classed, but are likely to be 

 moraines of the Fourth glacial stage.] . . 



[= Third Interglacial Stage, Durntenian of Geikie] 



Tyrrhenian Stage of Deperet. — "The entirety of the interglacial marine 

 deposits of temperate fauna corresponds, without doubt, to the Tyrrhenian 

 Stage of the Mediterranean with a shoreline of identical altitude (33 

 meters, maximum)" (Deperet, 1920.2). As the great Scandinavian 

 glacier again retired, the North Sea again approached the English coast, 

 and at Holderness (Prestwich, Reid) have been determined [Second 

 Interglacial] gravels and argillaceous marine sands intercalated between 

 the "lower Boulder-clay" and the "upper Boulder-clay." Beds corre- 

 sponding with the shoreline of 33 meters (100 feet) have been traced 



