257 described the lithological character and origin of the district. The Silurian beds consist of dark, glistening, foliated shales, gritty, arenaceous flagstones, micaceous, close grained, metamorphosed schists, fine conglomerates, and thin beds of argillaceous shalessome of which are highly ferruginous, and more or less altered by heat-nearly vertical and greatly disturbed. There is an apparent absence of intrusive rocks; the conformation of the surrounding hills and the intervening valleys

more »

... aves little room to doubt that the former have been divested of an immense thickness of once over lying strata, and the latter scooped out by some powerful agent. The missing strata are now found in the sands, gravels, clays, moraines, and detritus of the neighbourhood, and the denuding agent was doubtless land ice. He stated the two theories of glacial action, giving the preference to the more modern one suggested by Agassiz, which would account for the present con formation of the district of the Enterkin. He considered the Enterkin and the Merinoch valleys as the tracts of a pair of glaciers originating on the Lowthers and terminating in the valley of the Nith.