556 BEPORT — 1889. 



of the ice circle round the southern coasts of Norway, whence they sweep 

 south-east by east across the province of Gottland in Sweden, passing through the 

 lower ends of Lakes Wener and Wetter, while similar moraines mark out for us the 

 terminal front of the inland ice in Finland— at least two parallel frontal moraines 

 passing inland from Hango head on the Gulf of Finland through the southern part 

 of that province to the north of Lake Ladoga. Further north-east than this they 

 have not been traced ; but, from some observations by Ilelmersen, Sederholm 

 thinks it probable that the terminal ice-front extended north-east by the north of 

 Lake Onega to the eastern shores of the White Sea. Between Sweden and Fin- 

 land lies the basin of the Baltic, which at the period in question was filled with 

 ice, forming a great Baltic glacier, which overflowed the Aland Islands, Gottland, 

 and Oland, and which, fanning out as it passed towards the south-west, invaded, 

 on the south side, the Baltic provinces of Germany, while, on the north, it crossed 

 the southern part of Scania in Sweden and the Danish islands to enter upon 

 Jutland. 



The upper boulder-clay of those regions is now recognised as the ground-moraine 

 of this latest ice-sheet. In many places it is separated from the older boulder-clay 

 by interglacial deposits, some of which are marine, while others are of fresh-water 

 and terrestrial origin. During interglacial times the sea that overflowed a con- 

 siderable portion of North Germany was evidently continuous with the North Sea, 

 as is shown not only by the geographical distribution of the interglacial marine 

 deposits, but by their North Sea fauna. German geologists generally group all the 

 interglacial deposits together, as if they belonged to one and the same interglacial 

 epoch. This perhaps we must look upon as only a provisional arrangement. 

 Certain it is that the fresh-water and terrestrial beds which frequently occur on the 

 same or a lower level, and at no great distance from the marine deposits, cannot in 

 all cases be contemporaneous with the latter. Possibly, however, such discordances 

 may be accounted for by oscillations in the level of the interglacial sea — land and 

 •water having alternately prevailed over the same area. Two boulder-clays, as we 

 have seen, have been recognised over a wide region in North Germany. In some 

 places, however, three or more such boulder-clays have been observed overlying 

 one another throughout considerable areas, and these clays are described as being 

 distinctly separate and distinguishable the one from the other.' Whether they 

 with their intercalated aqueous deposits indicate great oscillations of one and 

 the same ice-sheet — now advancing, now retreating — or whether the stony clays 

 may not be the ground-moraines of so many difierent ice-sheets, separated the one 

 from the other by true interglacial conditions, future investigations must be left to 

 decide. 



The general conclusions arrived at by those wlio are at present investigating 

 the glacial accumulations of Northern Europe may be summarised as follows : — 



1. Before the invasion of Northern Germany by the inland ice the low grounds 

 bordering on the Baltic were overflowed by a sea which contained a boreal and 

 arctic fauna. These marine conditions are indicated by the presence under the 

 lower boulder-clay of more or less well-bedded fossiliferous deposits. On the same 

 horizon occur also beds of sand, containing fresh-water shells, and now and again 

 mammalian remains, some of which imply cold and others temperate climatic con- 

 ditions. Obviously all these deposits may pertain to one and the same period, or 

 more properly to diflerent stages of the same period— some dating back to a time 

 when the climate was still temperate, while others clearly indicate the prevalence 

 of cold conditions, and are therefore probably somewhat 5'ounger. 



2. The next geological horizon in ascending order is tliat which is marked 

 by the * Lower Diluvium ' — the glacial and fluvio-glacial detritus of the great ice- 

 sheet which flowed south to the foot of the Harz IMouutains. The boulder-clay on 

 this horizon now and again contains marine, fresh-water, and terrestrial organic 

 remains, derived undoubtedly from the so-called preglacial beds already referred to. 

 These latter, it would appear, were ploughed up and largely incorporated with the 

 old ground-moraine. 



' H. Schroder : Jahrh. d. k.prevss. geol. Landesaiutalt fiir 1887, p. 360. 



