J. Croll. — Boulder-clay of Caithness. 273 



not by local glaciers, is apparent from the fact observed by Eobert 

 Chambers, ^ that the general direction of the groovings and striae on 

 the rocks, beai-s little or no relation to the conformation of the 

 surface, showing that the ice was of sufficient thickness to move 

 straight forward, regardless of the inequalities of the ground. 



At Gottenburg, on the shores of the Cattegat, and all around 

 Lake Werner and Lake Wetter, the ice-markings are of the most 

 remarkable character, indicating in the most decided manner that the 

 ice came from the interior of the country to the north-east in one 

 vast mass. All this mass of ice must have gone into the shallow 

 Cattegat, a sea not sufficiently deep to float even an ordinary glacier. 

 The ice coming off Gothland would therefore cross the Cattegat, and 

 thence pass over Jutland into the North Sea. After entering the 

 North Sea, it would be obliged to keep between our shores and the 

 ice coming direct from the western side of Scandinavia. 



But this is not all, a very large proportion of the Scandinavian ice 

 would pass into the Gulf of Bothnia, where it could not possibly 

 float. It would then move south into the Baltic as land-ice. After 

 passing down the Baltic, a portion of the ice would probably move 

 south into the flat plains in the north of Germany, but the greater 

 portion would keep in the bed of the Baltic, and of course turn to 

 the right round the south end of Gothland, and thence cross over 

 Denmark into the North Sea. That this must have been the path of 

 the ice is, I think, obvious from the observations of Murchison, 

 Chambers, Horbye, and other geologists. Sir Roderick Murchison 

 found — though he does not attribute it to land-ice — that the Aland 

 Islands, which lie between the Gulf of Bothnia and the Baltic, are 

 all striated in a north and south direction.^ 



Upsala and Stockholm, a tract of flat country projecting for some 

 distance into the Baltic, is also grooved and striated, not in the 

 direction that would be effected by ice coming from the interior of 

 Scandinavia, but north and south, in a direction parallel to what 

 must have been the course of the ice moving down the Baltic. ^ 

 This part of the country must have been striated by a mass of 

 ice coming from the direction of the Gulf of Bothnia. And that 

 this mass must have been great is apparent from the fact that 

 Lake Malar, which crosses the country from east to west, at right 

 angles to the path of the ice, does not seem to have had any 

 influence in deflecting the icy-stream. That the ice came from the 

 north and not from the south is also evident from the fact that the 

 northern sides of rocky eminences are polished, rounded, and ice- 

 worn, while the southern sides are comparatively rough. The 

 northern banks of Lake Malar, for example, which, of course, face 

 the south, are rough, while the southern banks, which must have 

 ofiered opposition to the advance of the ice, are smoothed and 

 rounded in a most singular manner^ 



1 Tracings of the North of Europe, 1850, pp. 48-51. 

 ^ Quart. Jour. Geol. See, vol. ii. p. 364. 



^ Tracings of the North of Europe by Robert Chambers, pp. 259, 285. Observa- 

 tions 6ur les ph^nomenes D'Erosion en Norwege, by M. Horbye, 1867. 



