174 PREHISTORIC EUROPE. 



It was not until Agassiz visited Scotland and pointed out 

 the evidence for the former existence of glaciers in that country 1 

 that British geologists were put upon the right scent. For some 

 years before this time, however, it had been ascertained that a 

 cold climate had prevailed in Scotland during a very late Tertiary 

 period. The late Dr. Thomas Thomson had discovered and 

 described those beds of fossil mollusca on which so much of the 

 evidence of the Glacial Era depends, and four years later appeared 

 the first of a series of well-known papers by Mr. Smith of 

 Jordanhill, in which the same phenomena are discussed, and an 

 allusion made to Thomson's discovery. 2 After this time our 

 knowledge of the glacial phenomena, thanks to the labours of 

 Buckland, 3 Lyell, 4 J. D. Forbes, 5 Maclaren, 6 Chambers, 7 and 

 others, rapidly increased. The theory of ddbdclcs was laid aside, 

 but a belief that a large part of the phenomena could only be 

 accounted for by enormous submergences of the land continued 

 for many years to hold possession of geologists, and still lingers 

 on amongst some observers whose attention has perhaps been too 

 exclusively confined to the low grounds of England. But the 

 notion of " waves of translation " has long disappeared. Those 

 who still cling to the view that much of the clay with far- 

 travelled stones which covers such wide areas in the lowlands 

 of Britain and the Continent is of marine origin, readily admit 

 the former existence of glaciers in the hillier regions ; but they 

 maintain that a large proportion of the erratics and stony clay 

 has been distributed during a period of submergence through 



1 Proc. Geol. Soc, vol. iii. p. 327 ; Edin. New Phil. Jour., vol. xxxiii. p. 217. 



2 See Obituary Notice of Dr. Thomson by Sir Joseph Hooker, Journ. Royal 

 Geogr. Soc, vol. xlviii. p. cxxxvii. Thomson's paper appears in Records of General 

 Science, vol. i. p. 131, February 1835. Glacialists are indebted to Sir Joseph 

 Hooker for calling their attention to this paper, which has been quite overlooked. 



3 Proc. Geol. Soc., vol. iii. pp. 332, 345 ; Edin. New Phil. Journ. vol. xxx. pp. 

 194, 202. 



4 Proc. Geol. Soc, vol. iii. p. 337 ; Edin. New Phil. Journ., vol. xxx. p. 199. 



5 Edin. New Phil. Journ., vol. xl. p. 76. 



6 Ibid. vol. xl. p. 125 ; vol. xlix. p. 333 ; Brit. Assoc. Rep., p. 90 ; and other 

 papers. 



7 Many papers in Edin. New Phil. Journ., Brit. Assoc Rep., and Proc. Royal 

 Soc. Edin., from 1850. 



