Until of late years, the South Wales coal-field was considered to be very barren in fossils, and those few which were known were all thought to be of land or fresh-water origin. During my endeavours to work out the geology of this district for the last four years, I have, however, discovered sufficient to redeem it from such a reproach, and to prove that not only are there fossils, but that these are even in great numbers and variety.

The basin, which occupies portions of Monmouthshire, Glamorganshire, Breconshire, and Carmarthenshire, may be separated into two great divisions, both geologically and chemically. The first is the division into upper and lower coal-measures, separated by a thick mass of Pennant sandstone, or grit, while the chemical is the division into bituminous and anthracitic coals. The upper measures are principally found in Glamorgan and Carmarthenshires, the only coal-seam of that series in Monmouthshire, being known as the Mynyddswlyn vein. Westward of the Taff, however, which is the boundary between the two countries, the upper measures appear more frequently, and in more regular sequence; while, in Carmarthenshire, we obtain a complete section of these beds down to the Pennant rock, in the neighbourhoods of Llanelly, Penllergare, and Lloughor. The middle, or Pennant rock series attains its greatest development at Swansea, where it is 3,000 feet in thickness, and presents several important beds of coal; but in the eastern portion of this field they are very much thinner, and contain little or no workable coal. The summits of the hills which bound the parallel valleys on the north crop, are nearly all capped with this grit, which adds much to the peculiar configuration of the country, and gives a certain identity of outline to its general features.

The next division, 8th, consists of a bed of fawn-coloured sandstone of about ten feet in thickness, containing nodules of rag, with Pectines, Terebratulæ, Rhynchonellæ, &c., in the lower portion, which, owing to its softness and looseness of texture, the weather wears away, leaving the shells finely exposed. It is chiefly owing to such excavation of this bed, by the combined influence of the elements, that those great falls of the superincumbent masses have taken place at intervals along the line of the Undercliff, many such “founders” having happened within the memory of residents, and others being likely to occur constantly from this hard and solid mass of strata resting on an insecure foundation, the effects of which are still further increased by the presence of the Gault below.

But a few years back a large mass near Blackgang thus assumed such a dangerous and threatening attitude, by the lower part of it being so much worn away, that the authorities blew it down with gunpowder. Many thousand tons of rock and debris were thus thrown down, completely blocking up and destroying the original road; one huge mass still stands close to the road, as large and as high as a good-sized cottage.

A layer of rag-stone, called the “Big Rag-bed,” containing fossils, terminates what is termed the “sandstone-group.”

In the preceding exposition the object has been to give, in a condensed form, the leading facts and conclusions of geology. These facts are so firmly established by observation, and the conclusions from them so clearly demonstrated, that every rational mind must assent and be prepared to admit the principle on which Geology, like all physical sciences, must rest—that geological phenomena must be referred to physical causes.

When the student has obtained sufficient familiarity with these established propositions, he will be prepared to follow in the discussion of the less elementary problems of the science, many of which are subjects of controversy. Before, however, going into these speculations, Mr. Hopkins devotes several pages to the evidences of the vast antiquity of the globe, dwelling both on the evidences afforded by the organic remains of successive creations embedded in the rocks, and on those drawn from the inanimate kingdom. Of the first we find that an immense number of different tribes of animals and plants which in former ages have given their passing phases to terrestrial life on our planet have disappeared with a transition so slow that, according to the present order of nature, there is not the slightest evidence of the introduction of a new species of animal since the creation of man; whilst of the latter, it appears certain that the deposition of sedimentary strata, and that process of denudation necessarily contemporaneous with it, must have proceeded at very much the same rate in former as in recent times; and, admitting this conclusion, we obtain something like a rough conception of the enormous lapse of time necessary for the deposition of the whole mass of sedimentary formations, by simply comparing such mass with the proportion which has been transported and deposited, within the last two or three thousand years.