412 MK. F. W. HAEMER ON THE [Aug. IQOI, 



Pliocene Epoch, resembling that of the Mediterranean or even the 

 Azores, but as the Great Ice Age approached and the climate 

 became colder, the Crag area was invaded by boreal and arctic 

 mollusca, and such forms, at first gradually, and at length entirely, 

 supplanted the southern shells. Early in the Bed Crag period, 

 species such as Natica clausa, and later on, those like Carciium 

 groenlandicum, Tellina calcarea, and Astarte horealis, now found 

 only to the north of the Arctic Circle, had established themselves in 

 the German Ocean as far south as lat. 52° N. We may therefore 

 conclude, I think, that the climate of regions to the north of Great 

 Britain had, in all probability, by that time become considerably 

 colder than now, and therefore frequently anti cyclonic in winter, an 

 ice-sheet having permanently established itself on the Scandinavian 

 highlands. This being the case, cyclones would have then been 

 diverted to the south of the course which now they usually take 

 at that season, and easterly rather than westerly gales would have 

 been prevalent in the Crag area.^ 



This matter, comparatively unimportant in itself, seemed to open 

 the way to enquiries of wider scope and of considerable interest.^ 



It is not only dead shells, for example, that are now blown 

 towards the shores of Holland by westerly gales. Extensive 

 sandbanks exist off the Dutch coast, whence material is trans- 

 ferred to the beach, and thence is blown inland to form immense 

 dunes, some of them, as in the island of Texel, being more than 

 2 miles wide. In Norfolk, on the contrary, the few sand-dunes 

 that exist are very narrow, and their preservation is a constant 

 source of anxiety to the local authorities. The 10-fathom line hugs 

 the English coast very closely, but it extends a considerable 

 distance, sometimes 10 miles, from that of Holland. 



Similar conditions exist in the Irish Sea, which is shallower 

 near its eastern than its western margin.^ Although partly due 

 to other causes, the piling-up of sediment in the Irish and the 

 North Seas on the one side rather than on the other must be 

 chiefly attributed, I think, to the action of the winds now pre- 

 valent, and, if so, it may be worthy of consideration how far the 

 varying thickness of some of the deposits of former periods may 

 have been caused in a similar way. 



The establishment of a permanent ice-sheet, the meteorological 

 conditions of which may have been more or less prevalently anti- 

 eyclonic, first over Scandinavia, and at a later period over the 

 British Isles and a great part of Northern Europe, together with 

 the former existence of similar ice-fields (on an even more extensive 

 scale) in North America, assuming that such an explanation of the 



^ A preliminary note on this subject, published in short abstract only, was 

 presented to the Meeting of the British Association at Dover in 1899 ; see 

 Brit, Assoc. Eeport, p. 753, 



^ See also M, Paul Tutkowski's -views on the origin of loess, Scot. Geogr. 

 Mag. vol, xvi (1900) p. 171. 



^ See Map in 10th Annual Report of the Liverpool Marine Biology 

 Committee (1897) p. 17. 



