280 PROCEEDINGS OF THE GEOLOaiCAL SOCIETY. [May 12, 



pointed to the metamorphic character of granite ; and in some parts 

 of Corsica this was still more plainly shown than in Devonshire. 



Mr. W. W. Smyth agreed that the disintegration of granite was 

 mainly due to the causes pointed out by the author. He did not, 

 however, regard them as entirely resulting from subaerial denuda- 

 tion acting on a surface of uniform quahty. There was probably a 

 difference in the proportions of the constituent parts in the granite, 

 some parts in the same quarry being soft while others were of ex- 

 treme hardness. These softer parts were easily removed, while the 

 harder parts were left. The question was, whether this difference 

 was the result of the original deposition or of subsequent segrega- 

 tion. Even where china clay resulted from the decomposition of 

 the rock, some of the nodules of harder granite occurred. 



Prof. Brayley remarked that the subject of the spheroidal struc- 

 ture of some of the crystalline rocks was of much importance in 

 geological physics. He believed he had been the first to call atten- 

 tion (Phil. Mag. 1830) to the connexion of rock-basins with that 

 structure as existing in granite. The phenomena at Karn Bre in 

 Cornwall were much the same as on Dartmoor, and resulted, ori- 

 ginally, from the concealed spheroidal structure of the rock, or 

 rather from what he might term a spheroidal tension. In Mount- 

 Sorrel syenite and Northumberland basalt the same was to be traced ; 

 and Eowley Eag exhibited the effect of the spheroidal tension, as 

 developed by weathering, in the most perfect manner. 



Mr. Scott stated that in the granite district near Dubhn isolated 

 blocks, deeply weathered, like the tors described in the paper, were 

 met with. The granite itself contains masses of a harder nature 

 than the surrounding rock, which are usually enveloped in a coating 

 of black mica. In the stratified granites of Donegal and Argyllshire 

 such a structure had never been noticed by him. 



2. Notes on Apparent Lithodomous Perforations in North-west 

 Lancashire. By D. Mackintosh, Esq., F.G.S. 



[Abridged.] 



The author, after referring to the discovery of perforations in lime- 

 stone rocks, at various altitudes above the sea, by Mr. Pengelly in 

 Devonshire and Mr. Darbishire in North Wales, proceeded to de- 

 scribe the character and mode of occurrence of those he lately 

 observed near the shores of Morecambe Bay. They were stated to 

 be most numerous in the neighbourhood of Great Urswick, at alti- 

 tudes of between 200 and 300 feet ; but after a persevering search 

 he found them on the eastern or Grange side of Hampsfell up to 

 667 feet above the sea. " They occur in limestone rocks of varying 

 structure. . . . They have been excavated irrespectively of any hard- 

 ness or softness of the rock, and of any susceptibility to decay in 

 one part of the rock more than another. Their circumference runs 

 continuously through portions of rock of varying composition," and 

 the holes often run into and through fossils. 



