562 Notices of Memoirs — A. Gilligan, 3Iilktone Grit, York.s. 



but too much decomposed to be accurately identified. The pieces of 

 granite were composed of quartz and felspar, suggesting by their 

 appearance derivation from coarse-grained granites. Pebbles of quartz 

 he found to be commonest, and he also described sonje pieces of white 

 or brownish orthoclase felspar. 



The granites he found were quite unlike any with which he was 

 acquainted in the British Isles, being too coarse and much more like 

 those oi: Scandinavia. Further, the current-bedding, which Dr. Sorby 

 examined over an area of twenty-five square miles, pointed to a drifting 

 from the north-east, and he therefore suggested some south-westward 

 prolongation of an ancient Scandinavia as the source of origin of the 

 material making up the great mass of the Millstone Grit of Yorkshire. 

 Since this early work by Dr. Sorby nothing has been added to our 

 knowledge of the lithology of this, to most people, uninteresting series 

 of rocks. The late Mr. A. Longbottom, B.A.,. of the Nigerian Survey, 

 collecterl some very large pebbles from the Middle Grits of Silsden. 

 These have been examined by the author, who has also extended hia 

 researches into the other beds of the series in various parts of 

 Yorkshire. Some of the pebbles are of a very large size, one obtained 

 from Netherwood Plantation Quarry, Silsden, measures 10 inches by 

 8 inches by 3 inches, and is a reddish granitoid rock with large 

 porphyritic felspar. The pebbles show a remarkable assemblage of 

 rocks, igneous, sedimentary, and metamorphic all being represented, but 

 by far the commonest are acid igneous rocks — granites, quartz, and 

 felspar porphyries. Only one specimen of basic igneous rock has been 

 found. The metamorphic rocks are quartz-schist and mica-schist, with 

 a few fragments of gneiss. One of the mica-schist pebbles has been 

 identified by Mr. Barrow as similar to a rock described by him occurring 

 in the Moine Schists of the East Central Highlands. Numerous pebbles 

 of felspar have been examined by the author, and in each case found 

 to be perfectly fresh microcline, the cross-hatching being beautifully 

 clear. Pieces of pegmatite, the constituents being quartz and microcline, 

 are very common in all the beds, but most abundant in the Kinderscout 

 Grit and Rough Hock. Some fragments obtained from the Plompton Grit 

 at Knaresborough proved to be a peculiar silicified oolitic rock, the 

 outlines of the oolitic grains being traced out by small rounded bodies 

 stained red or brown. A few pebbles show undoubted traces of 

 organisms such as sponge spicules, etc. 



The heavy minerals of the grit are not numerous, the most plentiful 

 being zircon and garnet. The felspar in the grit, both large and small, 

 are quite fresh when first exposed, and this suggests either disintegration 

 of the parent rock by diiferences of temperature and rapid transporta- 

 tion, or comparative absence of carbon dioxide in the atmosphere. The 

 author has been much impressed by the many points of similarity 

 existing between the Millstone Grit and the Torridon Sandstone, and i? 

 disposed to think that areas of similar rock types were laid under con- 

 tribution for each. 



III. — The Silurian Inlier of Usk.' By C. I. Gardiner, M.A., F.G.S. 



THE Usk Inlier is roughly oval in shape, measuring about eight miles 

 and a half from north to south and four miles from east to west. 

 It is crossed by an important east and west fault, which divides it into 

 two nearly equal parts. The southern half is composed of two anti- 

 clines separated by a fault. The axes of these folds run roughly north 

 and south, and dip southwards. The western anticline is the larger of 

 the two, and shows Wenlock Shales and Limestone and Ludlow Beds ; 

 these are all very fossiliferous. 



' Abstract of paper read before the British Association, Section C (Geology), 

 Dundee, September, 1912. 



