Mr Murchison on the Glacial Theori/. ItM 



cumulated beneath the waters of former days. Throughout large tracts 

 of England we can demonstrate this to have been the case by the collo- 

 cation of marine shells of existing species with far transported materials. 

 It was the association of these testacea with foreign blocks in the cen- 

 tral counties of England which first led me to attach a new and sub- 

 stantial value to that view of glacial action which had been so well ad- 

 vocated by Mr Lyell before Professor Agassiz came forward with his 

 great terrestrial and general theory. I am bound to say, that wide re- 

 searches during the last two years have strongly confirmed my early 

 views.* I could not travel, in the autumn of the year 1840, around the 

 shores of the Highlands of Scotland, without being convinced that the 

 terrace upon terrace, presented on the sides of some of the great valleys, 

 and often high up on the sea-ward hills of the bays opening out to the 

 ocean, were nothing more than the bottoms of former seas and estuaries 

 which had been successively desiccated. 



I coincide, therefore, entirely with Mr C. Darwin in his very ingenious 

 explanation of the probable fonnation of the parallel roads of Glen Roy 

 (Phil. Trans., 1839, p. 39). Since then, that excellent observer has 

 borne out similar views in a paper read before our owh Society. In this 

 memoir, estimating the difTerent changes of the sea and laud, and shew- 

 ing to what extent the solid strata were depressed, whose relative histories 

 he thus reads off, he traces the shingle beds from the edge of the sea, 

 where they are in process of formation, to considerable heights inland ; and 

 estimating how blocks were transported from the great Cordillera within, 

 or not long before the period of existing sea shells, he explains the far- 

 transported boulders by their being carried to the ports where they 

 lie in vessels of ice. The melting of these icebergs he conceives to 

 have been the chief agent in forming such masses of clay, gravel, and 

 boulders, as constitute the " till" of Scotland ; whilst the confusion and 

 contortion of their imperfect strata is considered by him to be necessarily 

 due to the grounding of icebergs in the manner formerly suggested b}' Mr 

 Lyell. To the same powerfully disturbing agent he attributes the general 

 absence of organic remains in these deposits ; and, lastly, he infers that 

 it is much more probable that the great boulders were transported in ice- 

 bergs detached from glaciers on the coast, than imbedded in masses of 

 ice produced by the freezing of the sea. 



M. de Yerneuil and myself had previously brought before you some 

 new results, arising from our first expedition to Russia. We endea- 

 voured to shew the utter inapplicability of the Alpine glacial theory to 

 vast regions of Northern Russia, though the surfaces of the rocks are 

 scored and polished, and far-travelled blocks occur throughout a wide 

 area in isolated groups, because much of this detritus has travelled over 

 extensive tracts of low country, from which it has ascended to levels 

 higher than the sources of its origin. Hence we inferred, that the on- 



* See Silurian Svstem. p. 530, 



