Page:Proceedings of the Royal Society of London Vol 1.djvu/261

Rh from 18 to 20 miles; but in Pembrokeshire its breadth is only from 3 to 5 miles.

On the northern half of the basin the strata rise gradually north- ward; on the south side they rise southward, except at the east end, where they rise eastward. The deepest part of the basin is between Neath, in Glamorganshire, and Llanelly in Carmarthenshire, where the depth of the principal strata of coal and iron ore is from 600 to 700 fathoms; whereas in Pembrokeshire, none of the strata lie above 80 or 100 fathoms deep.

The strata of coal at the east end of the basin and on the north side, are chieﬂy of a cokeing quality; but they alter, towards St. Bride’s Bay, to what is called stone coal: on the south side of the basin the strata are principally of a bituminous or binding quality.

In this mineral basin there are 12 veins, or strata of coal, from 3 to 9 feet thick; and 11 others, from 18 inches to 3 feet, making in all 95 feet, besides a number of smaller veins, from 6 to 18 inches in thickness.

There are in these strata many faults or irregularities, by which the due range of the strata is thrown out of course. These faults are not conﬁned to the edges of the strata, but run through the in- terior of the basin generally, in a north and south direction, and often throw the whole of the strata, for hundreds of acres together, 40, 60, 80, or 100 fathoms up or down. There is, however, seldom any su- perﬁcial appearance that indicates a disjunction; for the greatest faults frequently lie under even surfaces.

A very considerable fault is observable at Crib-bath, where the beds, or strata of the limestone, stand erect. Another fault of great magnitude lies between Ystradvellte and Penderryn, where all the strata, and the north side of the basin, are movcd many hundred yards southward.

The limestone appears at the surface, all along the boundary line, in the counties of Monmouth, Glamorgan, Carmarthen, and Brecon; and no doubt can be entertained that it ranges from Newton, across Swansea Bay, to the Mumbles, and from Canmaddock Hill, across Carmarthen Bay, to Langam Tenby. In Pembrokeshire it appears at the surface only in some particular spots; yet it certainly forms an under-ground connexion from one spot to the other.

Glamorganshire possesses by far the greatest portion of coal and iron ore; Monmouthshire is the next in point of quantity; then Car- marthenshire; then Pembrokeshire; and lastly Breclmockshire, which possesses the least.

The object of Mr. Robertson, who resided in Jamaica, as a King’s Surveyor of Land, upwards of twenty years, is to show that no