on the Rocks in the Environs of Edinburgh, 303 



we have now to examine, is a secondary one. Every one admits 

 that at a certain epoch the high valleys of Scotland were 

 occupied by permanent glaciers. According to the one 

 party, these glaciers descended to the shore of Ahe then 

 existing sea, and covered the Scottish lowlands, and were 

 in that condition in which we now find those of Spitzbergen 

 at the present day.* According to the other party, the 

 portion of Scotland which is comprised between the Frith of 

 Forth and the mouth of the Clyde was submerged under 

 the waters of the sea, and the icebergs detached from the 

 glaciers of the mountains floated upon the sea, and were 

 borne by a current which flowed from west to east. 



Examination of the Theory of Floating Icebergs. 

 It is indisputable that the relative levels of the land and 

 sea have undergone a change in a great portion of the coast 

 of Scotland. The terraces which bound the shore, and the 

 mollusca which are still living in the north sea. and whose shells 

 are still found at an elevation considerably above the highest 

 tides, incontestibly prove this. Messrs Prestwick and Craig 

 have pointed out those of the number which belong to living 

 species, reaching to an elevation of 360 feet, at Gamrie and 

 Airdrie, near Glasgow. t What, however, appears to me in 

 no degree demonstrated is, that this immersion actually 

 occurred during the glacial epoch. The direct contrary 

 would seem very much more probable, since the shells of 

 Gamrie are of the existing species, and are still found in the 

 neighbouring sea. But for the support of the hypothesis of 

 floating icebergs it is necessary to prove that the whole of 

 the flat land had been plunged under the water during the 

 cold period to a considerable depth : in fact, the polished rock 

 situated upon the southern side of Arthur Seat is not less 

 than 400 feet above the level of the sea. There is one on 



* See my Memoir upon the Glaciers of Spitzbergen. Edinburgh New Phil. 

 Jour., vol. XXX., p. 284. 1841. 



t Proceedings of the Geological Society of London, 1837, p. 649. And Mr 

 Smith, Jordanhill, Mem. Wernerian Society, vol. viii. The shells of Gamrie 

 f^re Astarte scotica, Tellina tenuis, Buccinum undatum, Natica glaucina, Fusus 

 turricola, Dentalium dentalis, &c. 



