GLACIAL SUCCESSION IN EUROPE. 133 



followed continuously over considerable areas. It is quite possible, of course, that all 

 those boulder-clays may be the product of one epoch, laid down during more or less con- 

 siderable oscillations of an ice-sheet. In this view of the case the intercalated aqueous 

 deposits would indicate temporary retreats, while the boulder-clays would represent 

 successive readvances of one and the same mer de glace. On the other hand, it is equally 

 possible, if not more probable, that the boulder-clays and intercalated beds are evidence 

 of so many separate glacial and interglacial epochs. We cannot yet say which is the 

 true explanation of the facts. But these being as they are, we may doubt whether 

 German glacialists are justified in so confidently maintaining that their lower and upper 

 diluvial accumulations are the products of the " first " and " second " glacial epochs. 

 Indeed, as I shall show presently, the upper diluvium of North Germany and Finland 

 cannot represent the second glacial epoch of other parts of Europe. 



For a long time it has been supposed that the glacial deposits of the central regions of 

 Eussia were accumulated during the advance and retreat of one and the same ice-sheet. 

 In 1888, however, Professor Pa vlow brought forward evidence to show that the province 

 of Nijni Novgorod had been twice invaded by a general mer de glace. During the first 

 epoch of glaciation the ice-sheet overflowed the whole province, while only the northern 

 half of the same region was covered by the mer de glace of the second invasion. Again, 

 Professor Annachevsky has pointed out that in the province of Tchernigow two types of 

 glacial deposits appear, so unlike in character and so differently distributed that they 

 can hardly be the products of one and the same ice-sheet. But until recently no inter- 

 glacial deposits had been detected, and the observations just referred to failed, therefore, 

 to make much impression. The missing link in the evidence has now happily been 

 supplied by M. Krischtafowitsch.* At Troizkoje, in the neighbourhood of Moscow, occur 

 certain lacustrine formations which have been long known to Russian geologists. These 

 have been variously assigned to Tertiary, lower glacial, postglacial, and preglacial 

 horizons. They are now proved, however, to be of interglacial age, for they rest upon 

 and are covered by glacial accumulations. Amongst their organic remains are oak 

 (Quercus jpeduncidata), alder (Alnus glutinosa, A. incana), white birch, hazel, Norway 

 maple (Acer platanoides), Scots fir, willow, water lilies (Nwphar, Nymphcea), mammoth, 

 pike, perch, Anadonta, wing-cases of beetles, &c. The character of the plants shows 

 that the climate of Central Eussia was milder and more humid than it is to-day. 



It is obvious that the upper and lower glacial deposits of Central Russia cannot be 

 the equivalents of the upper and lower diluvium of the Baltic coast-lands. The upper 

 diluvium of those regions is the bottom-moraine of the so-called great Baltic glacier. At 

 the time that glacier invaded North Germany, Finland was likewise covered with ice, 

 which flowed towards the south-east, but did not advance quite so far as the northern 

 shores of Lake Ladoga. A double line of terminal moraines, traced from Hango Head 

 on the Gulf of Finland, north-east to beyond Joensuu, puts this beyond doubt.t The 



* Bull, de la Soc. Imper. des Naturalistes de Moskau, No. 4, 1890. 



t Sederholm, Fennia, i. No. 7 ; Frosterus, ibid, iii., No. 8 ; Ramsay, ibid, iv., No. 2. 



