Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/288

 Harptree, Chewton Mendip, Stratton on the Fosse, Mells, and Elm on the north side, where it is a grand and significant feature in the physical structure of the flanks of the Mendip chain. In the words of De la Beche, " Standing on any of the high grounds on the Mendip Hills, it is interesting to consider how exactly the masses occur as they should do, under the supposition that they have been beaches among islands rising above the sea of the time."

Again, at Croscombe, Dinder, Wookey *, Westbury, Cheddar, and Compton Bishop it exhibits itself as a portion of a widely spread series to the south of the Men dips, beneath the Keuper and Lias of the plain of Somerset. The singular outliers of Gambarts Hill, Worminster, Knowle, and Church Hills south-east of Wells, islands of Carboniferous Limestone, now surrounded by dolomitic conglomerate and Red Sandstone, are evidences of what must be the deeper-seated condition of these beds under the plain of New Bed and Lias of Pennard and Glastonbury on the south, onwards to South Devon, extending, as I believe, to, and being of the same age as, the conglomerate, breccia, or pebble-beds of Budleigh-Salterton, and the sandstones containing Hyperodapedon.

I cannot, also, doubt that the remarkable breccias on either side of the Quantock Hills and in the vales of Stogumber and Wellington, which follow the tortuous course of the flank of the Exmoor, are all of this age.

I must not omit to notice the remarkable outlier of Broadfield Down, between Bristol and the Mendips ; for at no point around its island-like mass is it free from this encircling, reef-like, or fringing conglomerate. To attest still more its widely spread condition, I must also assert its continuous presence at the base of the Lower Secondary rocks which cover up, or conceal, the coal-measures of the Somersetshire coal-field, or that area occupied by these rocks between Bristol and the Mendip Hills, in a north and south direction, as well as east and west from Broadfield Down to Newton St. Leo, near Bath, thus giving an area of 140 square miles, the greater portion of which is, I doubt not, occupied by unexposed dolomitic conglomerate, generally or universally known and designated by the coal-miners as the " overlie," or " millstone," from its invariably occupying the same position below the Keuper series over the southern area, and covering the several members of the coal-measures (the Upper Coal-shale, Pennant, and Lower Coal-shale). In the narrow vale of Wrington, at Butcombe, between Winford on Broadfield Down and Blagdon at the north part of the Mendip Hills, it is also finely exposed, the superincumbent hills of Lias and Red Marls being cut down or denuded so as to expose the conglomerate.

Nowhere along the eastern side of the southern basin, except at Mells, at the S.E. or E. extremity of the Mendip range, are these rocks exposed or brought to the surface ; but here they conceal the junction of the coal-measures with the mountain-limestone abutting

this conglomerate.
 * The famous Hyaena-den and cavern of Wookey Hole are both excavated in