Prosser —Fossils in Millstone- grit. 107 
IV. Tse Fossinirerous CHARACTER OF THE MILLSTONE-GRIT AT 
SWEENEY, NEAR OSWESTRY, SHROPSHIRE. 
By W. Prosssr, F.G.S., M.R.C.P. 
HE Carboniferous rocks of Shropshire possess several peculiar 
features; and no member of the series shows these in a greater 
degree than the Millstone-grit, as seen on Sweeney Mountain, near 
Oswestry. Before discussing these features, it will not be amiss to 
detail briefly the character of this rock in other localities. It varies 
considerably in different places. For instance, in the Forest of Dean, 
it is a hard intractable rock. Such it is also in Glamorgan and Mon- 
mouthshire, where it is often seen in place under the Coal-measures, 
or in boulders on the hillsides. Varteg Hill, near Pontypool, is a 
most characteristic spot for it; that hillside being covered with masses 
of grit, of all sizes and shapes. ‘These masses are not unfrequently 
wholly made up of water-worn quartz-pebbles, occasionally as large 
as a hen’s egg, in a cement of sand and decomposed felspar. And 
although hundreds of houses, with their garden-walls, have been 
built of them, yet considerable areas of these boulders remain. Very 
large blocks of this rock may be seen on the southern flanks of the 
Black Mountains, Caermarthenshire, above the village of Cross-Inn. 
The Millstone-grit of the South-Welsh Coal-field, which goes by 
the name of ‘ Farewell Rock ’—from the fact that the miner on 
striking it bids farewell to coal, possesses the valuable property of 
being able to resist successfully for a length of time the action of 
most intense heat, and for this reason the ‘ hearths’ of iron-furnaces 
are constructed of it. 
In the Warwickshire Coal-field, the Millstone-grit ‘consists of a 
hard siliceous quartz-rock, with thin bands of interstratified shale’ 
(Howell; Mem. Geol. Survey, 1859). In Derbyshire and Lancashire 
the Millstone-grit series is more varied and extensive; often exhi- 
biting in one section beds of very different lithological characters,— 
bands of impure limestone, partings of shales, and beds of sand- 
stone, alternating with each other (see Hull and Green, Quart. 
Journ. Geol. Soc., No. 79). All these kinds of Millstone-grit, how- 
ever, agree in one particular, namely, that where the calcareous 
element is absent, the beds are unfossiliferous. 
The Millstone-grit of the Flintshire Coal-field, as seen at Sweeney 
Mountain, near Oswestry, differs from the above-mentioned in being 
highly fossiliferous. ‘The rocks consist, for the most part, of sand- 
stone, formed of very minute quartz-pebbles in a matrix of decom- 
posed felspar. Many of the beds are soft enough to be broken by the 
hand, while others have a moderate degree of hardness, and they gra- 
duate from cream to chocolate-colour. Some of the harder beds are 
quarried for general building-purposes ; and they are said to possess 
the valuable property of the Oolite of Caen—that of hardening on 
exposure to the air. After long exposure, this stone, like the New 
Red Sandstone of Cheshire, exhibits white crystalline markings, 
which often stand out in bold relief, like some curious hieroglyphic 
