1871.] JAMIESOX BAXFFSHIEE METAMOKPHIC ROCKS. 107 



should have been accumulated showing so little variety in character, 

 and without the occurrence of any large boulders or beds of conglo- 

 merate. Perhaps it may be explained by snj)posing it to have been 

 accumulated in the depths of the sea, off the mouth of a great river 

 like the Amazon, which may have been continually pouring in se- 

 diment, but with a current not suificient to carry large pebbles. 

 The slate, or fine argillaceous sediment, between the two great 

 masses of arenaceous strata may be accounted for by a subsidence of 

 the area of deposit into deeper and stiller water, where little except 

 the finer sediment would be floated. 



The E.ed (Cambrian) Sandstone and Conglomerate of the !N^orth- 

 west Highlands, which stretches for a hundred miles from S.W. 

 to N.E., with a comparatively narrow breadth in the opposite di- 

 rection, looks as if it had been accumulated along a shore-line which 

 was probably the coast of an ancient continent of the Laurentian 

 gneiss. This Cambrian Sandstone is overlapped on its eastern 

 border by the Lower Silurian schists and quartz -rocks of the High- 

 lands, which we may therefore suppose to have been accumulated 

 at a somewhat later period, but which, in all likelihood, consist of 

 the sediment poured into the sea by the rivers draining the same 

 Laurentian region to the north-west. After a great thickness of 

 sediment had been accumulated, a glow of heat from beneath seems 

 to have approached it, and by the expansion thereby occasioned 

 wrinkled the mass into huge folds running from S.W. to N.E. The 

 reason why the wrinkles run in that direction, I imagine, must be 

 that expansion in the transverse direction was more difficultj owing 

 perhaps to the opposing mass of the Cambrian and Laurentian 

 land preventing extension towards the north-west side. 



Discission. 



Prof. Rams-ay observed that the general section wonderfully corre- 

 sponded with that given many years ago by Sir Koderick Murchison 

 of the Silurian and Laurentian rocks at Cape Wrath, and it seemed 

 to him that the large views originally propounded by Sir Roderick 

 were confirmed by the author. He was glad that the metamorphic 

 origin of granite was supported by Mr. Jamieson, as he had held 

 that view for many years ; and he was pleased to find that opinions 

 which had formerly met with so many opponents were constantly 

 gaining acceptance. The fusion of these sedimentary rocks by meta- 

 morphic action was not identical with the fusion of lava ; but their 

 fluidity might be the same ; and if that were the case, there could 

 be no difficulty in accepting the possibility of the injection of such 

 fused rocks into crevices and fissures. The crumpling of the beds, 

 however, was due to more extensive causes than those contemplated 

 by t*he author. The proportion of igneous rock injected into con- 

 torted rocks, like those of North Wales, was comparatively small, 

 and the crumpling could hardly be due to mere local causes. 



Prof. Ansted referred to what he had observed in the north-west 

 part of Corsica, where about 40 feet of granite was distinctly inter- 



