﻿XC PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [May I908, 



attention to the smoothed and striated rock- surfaces now known as 

 roches moutonnees. After a study of them as displayed in 

 Scotland, he came to the conclusion that they can only have been 

 produced by sudden and violent debacles which, set in motion 

 by gigantic earthquakes and laden with mud and stones, swept 

 from the ocean across the face of the country.^ This opinion, or 

 some modification of it, continued to prevail for some thirty years. 

 Among those who, towards the end of that time, supported it was 

 the able mathematician William Hopkins. In a paper which 

 he communicated to the Society in 1842, ' On the Elevation & 

 Denudation of the District of the Lakes of Cumberland & West- 

 moreland,' he delivered an emphatic judgment against any glacial 

 theory, whether of glaciers or icebergs. He looked upon the 

 boulders scattered over the district as proofs of dispersal by waves 

 caused by sudden upheaval of the sea-bottom, and he thought that 

 this explanation completely removed the difficulties of the subject.^ 

 A few years of further consideration, however, led this convul- 

 sionist to revise his confidently expressed conviction, and the 

 change of view to which the accumulating evidence brought him 

 illustrates the general transformation of opinion which was then 

 in progress throughout the country, as the result of the publica- 

 tion of the group of papers above mentioned. 



At the beginning of last century Playfair, with that philosophic 

 insight which so distinguished him, pointed out that the most 

 powerful agency in nature for the transport of large masses of rock 

 is that of glaciers.^ But the indiclition which he thus supplied was 

 long lost sight of amid the strife of contending schools. N^obody 

 dreamt that glaciers could ever have existed in these islands, or 

 that, if they did exist among our mountains, they could ever have 

 crept down across the plains and hills of the lowlands, carrying 

 thither the debris of the higher grounds. That the climate around 



^ * On the Revolutions of the Earth's Surface ' Trans. Roy. Soc. Edin. vol. vii 

 (1812-14) p. 139. It should be remembered, however, that in the same year 

 Col. Imrie, in his paper on the Campsie Hills (Mem. Werner. Soc. vol. ii, 

 p. 35) had noticed the dressed surfaces of the trap-rocks of that district, and 

 looked on them as evidence of the general movement of a current from the west. 



2 Only an abstract of this paper appeared at the time in the Proceedings 

 (vol. iii, p. 757), but it was afterwards printed in full in vol. iv of the Quarterly 

 Journal (1848). It may be remembered that a similar explanation of the 

 erratics of the Jura and the southern slope of the Alps was published many 

 years earlier by Scrope in his ' Considerations on Volcanoes ' 1825, p. 217. 



3 ' Illustrations of the Huttonian Theory ' 1802, § 349. 



