798 REPORT—1896. 
ridges running across the island in a more or less east and west direction mark the 
outcrops of massive basalts, felsites, and hard felsitic conglomerates, the lower 
ground between them being formed of softer sedimentary strata, or of more thinly 
bedded rocks of basaltic character. 
1V. Age of the Rocks.—No fossils have yet been found on Skomer, but along 
the south side of the promontory at Wooltack Park, on the mainland, some grits 
and shales occur, containing tentaculites, &c., which closely resemble those of 
Skomer, and have the same general dip. ‘These beds are mapped by the Survey as 
Llandeilo, but are probably somewhat later in age. We are therefore inclined to 
regard the corresponding beds on Skomer, with their associated igneous rocks, as 
of Bala or Llandovery age. 
V. Microscopic Characters of the Rocks. (a) SEDIMENTARY.—The grits consist 
of clear quartz grains, with the angles rounded off, a felspar weathered beyond 
recognition, and, rarely, some mica. A granite pebble from the conglomerate 
ridge comes from the same mass as the Brimaston granite. (4) Frnsires.— 
Several of the slides show good flow structure, with phenocrysts of felspar, some- 
times largely kaolinised. A section cut from the more coarsely spherulitic part of 
the rock to the east of Tom’s House shows five well-marked whitish spherules (of 
about 2-inch diameter) in a greenish granular ground. The spherules are much 
cracked, and show dusty brown material in concentric bands towards the edges. 
Under crossed Nicols a well-marked fibrous radiating structure is apparent, but the 
crystallisation is somewhat confused, and the spherules do not show a clearly 
defined black cross. In two places the slide shows patches of crystalline character, 
which appear to be basaltic inclusions. (c) Basatrs anD PorPpHyrites.—The 
slides cut from specimens obtained from the west side of Tom’s House, the cave at 
the bottom of the Wick, the west side of South Haven, and from North Castle, all 
show porphyritic felspars, often with good crystal outlines, granules of augite, and 
much ilmenite or magnetite. The rock from the Neck, opposite Midland Island, is 
a porphyrite, showing fine laths of plagioclase felspar, and much black granular 
material, probably ilmenite, with no phenocrysts. The Skomer Head rock is a 
basalt—ophitic in parts—with lath-shaped felspar crystals, much augite (some of 
which is quite fresh), magnetite or ilmenite, and greenish decomposition products. 
The basalt of the Pigstone Rock shows good phenocrysts of felspar in a fine-grained 
dusty ground-mass ; the augite is small, and mostly altered, The rock seen at the 
Table is a porphyritic basalt, with large felspars showing very distinct crystal out- 
lines, some olivine, a little augite, and numerous opaque granules of ilmenite. 
Some of the basalts (e.g., that north of Bull Hole) show distinct flow structure, 
the small lath-shaped felspars being seen to bend round larger crystals. 
6. Notes on Sections along the London Extension of the Manchester, 
Sheffield, and Lincoln Railway between Rugby and Aylesbury. By 
Horace B. Woopwarp, F.&.S., £.G.S. 
[Communicated by permission of the Director-General of the Geological Survey. ] 
Commencing at Willoughby, near Braunston, attention was drawn to cuttings 
in the Lower Lias, from the zone of Ammonites armatus to that of A. capricornus 
at Catesby. The Catesby tunnel was excavated partly in the higher beds of 
Lower Lias, and partly in the Middle Lias, zone of 4. margaritatus. The Marl- 
stone rock-bed occurred above the tunnel and was exposed at its southern 
entrance. At Charwelton a mass of Upper Lias was let down by a trough-fault 
between beds of Middle Lias. Gravel containing pebbles of chalk and derived 
Jurassic fossils occurred also at Charwelton. Sections of Upper Lias were noted 
at Woodford Halse and Banbury Lane, near Moreton Pinkney. 
Boulder Clay was first encountered south of Woodford Halse, the vale of 
Lower Lias not exhibiting any section of it, It covers considerable tracts of the 
higher grounds onwards towards Steeple Claydon, and is an extension of the East 
Anglian Chalky Boulder Clay. 
