Not a great many years ago the “bigwigs” in England were assembled in conclave, and the élite of science was called before them. There were a great many lumps of a blackish-brown substance on the table, and a great deal of smelling, and burning, and poking of the same black lumps by the same “bigwigs” and learned men. It was the great “Torbane Hill Coal” case.

“The point was in question, as all the world knows, To what the said substances ought to belong.”

Was it pure carbon? Was it carbonaceous shale? Was it shale without much carbon? Was it carbon without much shale? Was it bituminous shale? Was it coal-shale? Was it cannel? Was it coal?

We are afraid to say how many guineas were spent, or how many microscopes were busy in London and Edinburgh. But after all the question was simply this, “What is coal?” We are not going to try to give a definition; but if we can show our young readers (and there are, we hope, a good many of them) a few of the facts connected with the structure, contents, mode of formation, &c., of a coal-field, perhaps we may be able to answer the formidable query, “What is coal?” without calling in the aid of counsel, and our fee is—one shilling. As this is a Christmas lecture for our young friends, we hope our senior readers will not take it amiss if elementary phrases are introduced, and a few woodcuts given to illustrate what they know very well. And perhaps we may be allowed to speak in the first person singular; it is more conversational.

Some other memoranda which I find among my papers relating to this work (for a section of which, with particulars of shaft-sinking, see “Geologist” of last month) may not be unacceptable to your coal-mining readers.

The spot where the shaft was sunk was 476 feet above the level of the Severn Valley Railway at Eymoor, and about 510 feet above the ordinary height of the River Severn, from which it was distant about two miles. The coal seam met with and worked at the depth of 176 yards, has in other parts of the coal-field a thickness of four feet. The colliers regard it as a Flying Reed (red?) coal. Two of the thin coal-seams afterwards sunk through were entirely made up of the remains of Sigillariæ; the coal, in consequence, was “long grained” and slaty. These Sigillarian coals have a considerable range through the Wyre Forest field, and in common with most of the other seams, crop out along the western border. At the Baginswood pits, in the north-west corner of the coal·field, the upper coal, two feet four inches in thickness, worked by hand-draw, being only ten yards from surface, is a most interesting seam, made up entirely of compressed Sigillariæ.

When a mineral presents itself under a form which does not belong to it, there is then what I shall call pseudomorphism.

The substance from which the mineral borrows its form may be of any kind—inorganic or even organic. It is called original or pseudomorphosed, while the mineral which replaces it is called pseudomorphic.

Pseudomorphism by alteration is that in which the pseudomorphic mineral still contains the elements of the original substance. Pseudomorphism by displacement is that in which this is not the case. In order to understand the difference which exists between these two kinds of pseudomorphisms, it suffices to mention as examples ironpyrites, which changes into limonite, still preserving its crystalline form; or fluor, which after being completely destroyed, is replaced by quartz. The name of paramorphism has been given to the kind of pseudomorphism which is produced without modification of chemical composition. Arragonite changed into calcite, and pyrite changed into marcasite are examples.

At first sight it seems that these metamorphoses of minerals must be very exceptional, but observation teaches us, on the contrary, that they are met with in a number of localities; they are, moreover, extremely varied. In fact, they include all the alterations to which minerals are subject in their structure and in their chemical composition. They include also, as a particular case, the decomposition of minerals; and kaolin, for example, results from a true pseudomorphism of felspar.

We finished last month with the fact that plant-remains were found in plenty both above and below the coal. I shall draw your attention first to the roof-shale—or clay over the coal—“over-clay” as it is often called: for in this the great majority of remains are preserved.

In the roof-shale two kinds of plants are the most conspicuous—fern-leaves, and the diapered cylinders mentioned in our last. These are the prevailing fossils, though there are a great many besides.

Looking first at the fern-leaves, which from their beautiful forms cannot fail to strike the observer's eye, one is surprised to notice the extremely perfect state in which they occur. Delicate fronds, spread out as for the sheets of an herbarium, with hardly a leaflet disturbed from its true place, crowd the roof-shales of nearly all coal-mines. Dr. Buckland sang the praises of this beautiful tracery, which covers the roof of the mine, in glowing strains such as it will not do for a plain geologist to imitate. I have a lurking suspicion, however, that the great doctor conceived the passage not in the mine, but out of it.

At least one hundred and twenty species are known in our British coal-strata. So perfect are they occasionally, that the little fruit-patches (sori, as botanists term them), are found upon the backs of the fronds. This is not very common, except in one kind—the Pecopteris, which happens to be more abundant than most of the others, and in some species of this the fruit is found.

In the year 1851 I read a paper before the Geological Society “On the Superficial Accumulations and Surface-markings in North Wales,” in which I attempted to show that there had been two glacier epochs in that country, one before, and the other after the deposition of the boulder drift, which was ploughed out of some of the larger valleys by the secondhand smaller set of glaciers; and in a later work on the old glaciers of North Wales, I went further, showing that cold sufficient to form glaciers lasted during the whole time of submergence and emergence, both when the higher mountain-tops stood out of the sea as a cluster ofsmall islands, and afterwards when the whole land rose out of the water.

The first of these memoirs touched on several subjects not immediately connected with the glaciation of Wales, though bearing in a larger sense on the same Geological period, and on the same set of questions. This the Council of the Geological Society decided not to print in their Journal, on the ground that it was too speculative—an opinion with which, in a great measure, I now coincide. One question was, however, raised in this unprinted matter which I do not yet remember to have seen in any published paper, and I now mention it because of late the attention of many persons have been more and more drawn to the discussion of the subject.

One of the greatest and most significant laws which modern palæontology has unfolded to us, is that principle by which it is definitively ascertained that, as a general rule, the animals of the Post-Pliocene, and indeed all the later Tertiary ages, were restricted to the same great geographical provinces as their representatives in the existing fauna. Amongst the Pliocene Mammalia of South America, we find the same preponderance of the Edentata, the same family of prehensile-tailed Monkeys, and the same typical Llamas and Vicuñas, as we find in the present pampas of La Plata, forests of Brazil, or elevations of the Andes.

But we also find animals which, from all our previous pre-conceived associations, we had considered peculiar to the old world. The Elephants, of which one species (E. Africanus) now exists in Africa, a second (E. Indicus) in India, and a third (E. Sumatranus) in Sumatra and Ceylon, apart from the extensive and widely-distributed evidences which we find of their fossil remains in Europe, India, China, and Australia, extended their geographical province in the later Tertiary age over the whole of North America. The species of elephant which we find in Siberia (E. primigenius) has also been found over the whole of the space lately marked on our maps as the United States. South of the 30th degree of N. Iatitude it however gives place to a totally different species of true Elephant (Elephas Texianus, Owen, E. Columbi? Falconer), the molars of which, by their less degree of complexity, were more adapted to triturate the soft succulent herbage of Texas and Mexico. Besides these true Elephants, there existed in North America many individuals of the genus Mastodon, to which the present communication more particularly alludes.

Amiens and Abbeville do not, however, enjoy a monopoly in these flint implements; they are found, apparently, all over the earth. At any rate, we can boast in our land of such treasures, and we can proudly record that the first discovered specimens belong to England. Let Amiens and Abbeville by all means be commemorated as the scenes of M. Boucher de Perthes' persevering investigations, which have furnished the incitement to the present remarkable inquiry—let the names of Boucher de Perthes, Prestwich, Falconer, Flower, and Evans, be duly honoured as the pioneers of the investigation; but let us also think of Hoxne, Grays, Ilford, Maidstone, Stanway, and the scores of other places where mammalian bones have been found in our own land—and, let us hope that our young geologists will set to work, and reap a rich harvest in the yet ungarnered fields. Does not this first recorded implement—this earliest discovered relic—(fig. 5) treasured and preserved in the Sloane collection, the nucleus of the British Museum, and entered in that old catalogue, two hundred years ago—encourage them. Does it not say in unmistakable language “Under your feet these relies may be found?”

There is another of these spear-shaped flints, which has obtained a great deal of notoriety in the late discussions. It was found at Hoxne, in Suffolk—a place memorable in the history of the good king Edmund, the saint and martyr—and was described, and figured in the “Archæologia,” (see cut 9, p. 20), by Mr. Frere, the finder, who, with remarkable acuteness, seems to have fully comprehended the value and true bearing of his discovery. His paper is, even now, an excellent epitome of the subject; and we give it at length, just as it was read in 1797, before the Society of Antiquaries of London.