Prof. James Geikie’s Address. 467 
with the North Sea, as is shown not only by the geographical dis- 
tribution of the inter-Glacial marine deposits, but by their North Sea 
fauna. German geologists generally group all the inter-Glacial 
deposits together, as if they belonged to one and the same inter- 
Glacial 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 contem- 
poraneous with the latter. Possibly, however, such discordances 
inay be accounted for by oscillations in the level of the inter-Glacial 
sea—land and water having alternately prevailed over the same 
area. ‘T'wo Boulder-clays, as we have seen, have been recognized 
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 different ice-sheets, separated the one from the 
other by true inter-Glacial conditions, future investigations must be 
left to decide. 
The general conclusions arrived at by those who are at present 
investigating the glacial accumulations of Northern Europe may be 
summarized 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 conditions. Obviously all these deposits may 
pertain to one and the same period, or more properly to different 
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 younger. 
2. The next geological horizon in ascending order is that 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 Mountains. The Boulder-clay on this horizon now and again 
contains marine, fresh-water, and terrestrial organic remains, derived 
undoubtedly from the so-called pre-Glacial beds already referred to. 
These latter, it would appear, were ploughed up and largely incor- 
porated with the ground-moraine. 
3. The inter-Glacial beds which next succeed contain remains of a 
well-marked temperate fauna and flora, which point to something 
more than a mere partial or local retreat of the inland ice. ‘he 
geographical distribution of the beds and the presence in these of 
1 HH. Schréder, Jahrb. d. k. preuss. geol. Landesanstalt fur 1887, p. 360. 
