372 Geological Society. 



(3) consist of (a) coarse red porphyrite, (6) quartz porphyry, (c) 

 felsite, (d) granite. The author considers that the porphyrite and 

 granite (which are alternately intrusive one in another) belong 

 approximately to the same geological epoch. This is the Lower Old 

 Red .Sandstone ; and as pebbles of the granite as well as of the por- 

 phyrite occur in the Lower Carboniferous measures of the region, 

 great denudation must have taken place prior to the latter epoch. 

 The author also describes some basalt dykes which he considers to 

 be of Miocene age. 



March 8.— J. W. Hulke, Esq., F.R.S., 

 President, in the Chair. 

 The following communications were read: — 



1. "Additional Note on certain Inclusions in Granite." By 

 J. Arthur PhiUips, Esq., F.E.S., F.G.S. 



The author referred to certain rounded inclusions in granite which 

 were rich in mica. These he had described in his paper published 

 in vol. xxxvi. of the ' Quarterly Journal,' and had considered to be 

 contemporaneous segregations from the molten rock. He had, up 

 to that time, not found a case where one of the larger crystals of 

 felspar in a porphyritic granite occurred partly in the one, partly 

 in the other. Of late he had seen several, one of which he described 

 minutely, thus proving the correctness of his supposition. 



2. " The Geology of Madeira." By J. S. Gardner, Esq., F.G.S. 

 Madeira consists almost wholly of sheets of basaltic lava of 



variable thickness interstratified with tuff scoria? and red bole, cut 

 b} r innumerable dykes. In the central part of the island is a horse- 

 shoe-shaped valley, more than 4 miles in diameter, its bed 2500 feet 

 above the sea, its precipitous walls full 3000 feet high, rising here 

 and there to yet greater elevations, and forming a central point in 

 the mountain-system of the island. This the author regards as the 

 basal wreck of a volcanic mountain, blown into the air by an explo- 

 sion of exceptional violence. Fragments of the slopes of scoria) 

 which once composed the inner shell remain on the peaks surround- 

 ing this amphitheatre. The dykes here are trachyte. The author 

 describes a limestone exposed in ono place beneath the basalts and 

 referred to the Upper Miocene, and a plant-bearing bed associated 

 with them, containing fossils of species still living in the island, 

 some of which have been wrongly referred to extinct forms. In 

 conclusion the author remarked upon the almost infinite variability 

 of the genus Rubus and the difficulty of distinguishing its species. 



3. " On the Crag Shells of Aberdeenshire and the Gravel Beds 

 containing them." By Thomas F. Jamieson, Esq., F.G.S. 



4. " On the Bed Clay of the Aberdeenshire Coast, and the Direc- 

 tion of Ice-movement in that quarter." By Thomas F. Jamieson. 

 Esq., F.G.S. 



The author describes a red clay occurring in the eastern part of 

 Aberdeenshire, which differs in many important respects from the 



