Duke of Argyll — Trajp and Granite of Mull. 553 



Granite was originally a stratified rock, merely changed by intense 

 heat and pressure, and could not, therefore, be said to be eruptive in 

 the usual sense. 



Mr. E. A. Wiinsch said that he had accompanied Dr. Bryce in his 

 researches, but had arrived at very different conclusions. The posi- 

 tion maintained by Dr. Bryce that there were two granites of dif- 

 ferent ages — the fine grained erupted through the coarse grained — 

 was utterly untenable. All the granites of Arran he believed to be 

 of one age, and the difference in grain was merely owing to the dif- 

 ference in texture of the different strata previous to being metamor- 

 phosed into granite. 



The President also expressed an opinion that granite is not erupted 

 rock in the ordinary sense of the term. 



V. — On the Trap and Granite in the Island of Mull. By 

 His Grace the Duke of Argyll, K.T., D.C.L., F.E.S. 



BEN CRAIG, one of the lower shoulders of Ben More, exhibits 

 very clearly the passage of a rock, which looks like pure trap 

 into regular granite. At the base of the shoulder of the mountain, 

 which may be about 2000 feet high, it is a mass of fine-grained com- 

 pact granite. At the top it is a mass of tuff which weathers white, 

 and has a fracture like some kinds of trap. At an immense eleva- 

 tion this tuff contains many crystals of felspar, very distinctly 

 separated. A little lower down these crystals become more frequent, 

 a granitic rock appears, and then comes the regular granite. His 

 Grace could detect no distinct separation. The top of the mountain 

 is very white, the rock very shattered, some of it very light, with one 

 or two dykes passing through this trap-like mass. The dykes are of 

 a closer texture, with white crystals unlike the surrounding mass. 

 The whole structure of Ben More, in Mull, is full of interest. The 

 summit peak is of stratified rock — mica slate — and all the lower 

 shoulders are granite, or igneous rock becoming granite. 



VI. — On the Cambrian Eocks of Llanberis. By George 

 Maw, F.L.S., F.G.S. 



A CUTTING on the branch railway from Carnarvon, now in course 

 of formation, has exposed the structure of the Lower Cambrian 

 beds, the most complicated part of the series. Underneath the beds 

 worked for slates in the Dinorwic and Glyn Quarries, there occurs a 

 considerable thickness of a trap-like rock, obscurely banded with 

 dark olive green and dull buff, which rests unconformably on the 

 upturned edges of a still more ancient slate rock. Many of the 

 dark-green bands, interstratified with the workable slates of the 

 higher series, and which have been grouped with the Cambrian grits 

 and pebble-beds, contain isolated fragments of altered slate, and 

 wherever they are in contact with the blue or purjsle slates, a thin 

 course of altered green slate occurs at the junction. Towards the 

 lower part of the upper series in the Glyn Quarries, the green 

 matter occurs as thin bands, in contact with which the slate has been 



