The Glacial TJieoi-y. 587 



far-transported materials. It was the association of these testacea 

 with foreign blocks in the central counties of England which first 

 led me to attach a new and substantial value to that view of glacial 

 action which had been so well advocated by Mr. Lyell before Pro- 

 fessor Agassiz came forward with his great terrestrial and general 

 theory. I am bound to say that wide researches during the last two 

 }'^ears have strongly confirmed my early views*. I could not travel 

 in the autumn of the year IS+O 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 

 upon 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 in- 

 genious explanation of the probable formation 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 

 own Society. In this memoir, estimating the different changes of 

 the sea and land, and showing 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 spots 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 con- 

 fusion and contortion of their imperfect strata is considered by him 

 to be necessarily due to the grounding of icebergs in the manner 

 formerly, suggested by Mr. Lyell. To the same powerfully disturb- 

 ing agent lie 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 icebergs detached from 

 glaciers on the coast, than imbedded in masses of ice produced by 

 the freezing of the sea. 



M. de Verneuil and myself had previously brought before you 

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

 endeavoured to show the utter inapplicability of tiie 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 ori- 

 gin. Hence we inferred, that the onward persistent march ^in 

 many parts up-hill) of a body of glaciers, having a front of many 

 hundred miles in extent, is irreconcileable with any imaginable sub- 

 aerial action. On the other hand, it was proved, by the presence of 



* See Silurian System, p. 53G. 

 2 R2 



