21/6 J. Croll. — Boulder-clay of Caithness. 



to the observations of Eobert Chambers, seem to point towards 

 North Greenland. Is it possible that the entire Atlantic, from 

 Scandinavia to Greenland, was filled with land-ice ! Astounding as 

 this may at first appear, there are several considerations which 

 render such a conclusion probable. The observations of Chambers, 

 Peach, Hibbert, Allan, and others, show that the rocky face of the 

 Shetland and Faroe Islands has been ground, polished, and striated in 

 a most remarkable manner. That this could not have been done by ice 

 belonging to the islands themselves is obvious, for these islands are by 

 far too small to have supported glaciers of any size, and the smallest 

 of them are striated as well as the largest. Besides, the uniform 

 direction of the striae on the rocks shows that it must have been 

 effected by ice passing over the islands. That the striations could 

 not have been effected by floating icebergs at a time when the 

 islands were submerged is, I think, equally obvious, from the fact 

 that not only are the tops of the highest eminences ice-worn, but 

 the entire surface down to the present sea level is smoothed and 

 striated ; and these striations conform to all the irregularities of the 

 surface. This last fact Mr. Geikie has clearly shown is wholly 

 irreconcilable with the floating- ice theory.^ Mr. Peach ^ found 

 vertical precipices in the Shetlands grooved and striated, and the 

 same thing was observed by Mr. Thomas Allan on the Faroe Islands.^ 

 That the whole of these islands have been glaciated by a continuous 

 sheet of ice passing over them was the impression left on the mind 

 of Eobert Chambers after visiting them.* This is the theory which 

 alone explains all the facts. The only difficulty which besets it is 

 the enormous thickness of the ice demanded by the theory. But 

 this difficulty is very much diminished when we reflect that we have 

 good evidence, from the thickness of icebergs which have been met 

 with in the Southern Ocean,^ that the ice moving off the Antarctic 

 contiaent must be in some places considerably over a mile in thick- 

 ness. It is then not so surprising that the ice of the glacial epoch, 

 coming off Greenland and Northern Europe, should not have been 

 able to float in the North Atlantic. 



Why the Ice of Scotland was of sucJi Enormous ThicTcness. 



The enormous thickness of the ice in Scotland, during the glacial 

 epoch, has been a matter of no little surprise. It is remarkable how 

 an island, not more than 100 miles across, should have been covered 

 with a sheet of ice so thick as to bury mountain ranges more than 

 1,000 feet in height, situated almost at the sea- shore, while tracts of 

 country so near as the south of England and north of France, should 

 have escaped glaciation altogether. But all our difficulties disappear 

 when we reflect that the seas around Scotland, owing to their 

 shallowness, were, diiring the glacial period, blocked up with solid 

 ice. Scotland, Scandinavia, and the North Sea, would form one 

 immense table-land of ice, from 1,000 to 2,000 feet above the sea 



Glacial Drift of Scotland, p. 29. 



Geologicai, Magazine, vol. ii., p. 343. Brit. Assoc. Eep., 1864: (sections), p. 59. 



Trans. Roy. Soc, E4in., vol. vii., p. 265. 



Tracings of Iceland ^nd tl;e Faroe Islands, p. 49. 



Meteorological Papers published by the Board of Trade. No. 12. 1865. 



