132 PROFESSOR JAMES GEIKIE ON THE 



west, so as to invade on the south the Baltic provinces of Germany, while in the north 

 it traversed the southern part of Scania and overwhelmed the Danish islands as it spread 

 into Jutland and Schleswig-Holstein. The course of this second ice-sheet is indicated by 

 the direction of transport of erratics, &c, and by the trend of rock-strise and roches 

 moatonnSes, as well as by the position of its terminal and lateral moraines. 



Such, then, is the glacial succession which has been established by geologists in Scandi- 

 navia, North Germany, and Finland. The occurrence of two glacial epochs, separated by 

 a long interval of temperate conditions, has been proved. The evidence, however, does 

 not show that there may not have been more than two glacial epochs. There are certain 

 phenomena, indeed, connected with the glacial accumulations of the regions in question, 

 which strongly suggest that the succession of changes was more complex than is generally 

 understood. Several years ago Dr A. G. Nathokst adduced evidence to show that a great 

 Baltic glacier, similar to that underneath which the upper diluvium was amassed, existed 

 before the advent of the vast mer de glace of the so-called " first glacial epoch,"* and his 

 observations have been confirmed and extended by H. LuNDBOHM.t The facts set forth 

 by them prove beyond doubt that this early Baltic glacier smoothed and glaciated the 

 rocks in Southern Sweden in a direction from south-east to north-west, and accumulated 

 a bottom-moraine whose included erratics yield equally cogent evidence as to the trend 

 of glaciation. That old moraine is overlaid by the "lower diluvium," i.e., the boulder- 

 clay of the succeeding vast mer de glace that flowed south to the foot of the Harz — the 

 transport of the stones in the superjacent clay indicating a movement from N.N.E. to 

 S.S.W., or nearly at right angles to the trend of the earlier Baltic glacier. It is difficult 

 to avoid the conclusion that we have here to do with the products of two distinct ice- 

 epochs. But hitherto no interglacial deposits have been detected between the boulder- 

 clays in question. It might, therefore, be held that the earlier Baltic glacier was 

 separated by no long interval of time from the succeeding great mer de glace, but may 

 have been merely a stage in the development of the latter. It is at all events conceivable 

 that before the great mer de glace attained its maximum extension, it might have existed 

 for a time as a large Baltic glacier. I would point out, however, that if no interglacial 

 beds had been recognised between the lower and the upper diluvium, geologists would 

 probably have considered that the last great Baltic glacier was simply the attenuated 

 successor of the preceding continental mer de glace. But we know that this was not the 

 case ; the two were actually separated by a long epoch of genial temperate conditions. 



There are certain other facts that may lead us to doubt whether in the glacial 

 phenomena of the Baltic coast-lands we have not the evidence of more than two glacial 

 epochs. Three, and even four, boulder-clays have been observed in East and West 

 Prussia. They are separated, the one from the other, by extensive aqueous deposits, 

 which are sometimes fossiliferous. Moreover, the boulder-clays in question have been 



* Beskrifning. till geol. Kartbl. Trolleholm : Sveriges Geologiska Under sokning, Ser. Aa. Nr. 87. 



t Om de aldre baltiska isstrcimmen i sodra Sverige : Geolog. Forening. % Stockholm Forhandl., Bd. x. p. 157. 



