An examination of the constituent strata, and of the positions of these western coalfields, will lead to the induction that they have formerly been united, and that in Dean Forest we have a link between its larger neighbours, which has been preserved from denudation by its fortunately having been folded into a basin form. The twenty miles which intervene between Coleford and the Welsh hills exhibit only the Old Red sandstone, the base on which coal measures once rested, long since swept away by the wearing action of the sea, when the land has been raised after periods of submergence.

IRELAND. The coalfields of the sister country form a most interesting study to the geologist, but unfortunately yielding only a total annual quantity of 141,470 tons, present to the commercial or technical inquirer features of little present value and of no future prospects. He who has passed long days in exploring the hilly coal country of Carlow, Kilkenny, or Tipperary, -now examining the fossils of the shales, which remind him of those of the lowest coal series of central England, and anon looking down upon the wide plains of carboniferous limestone which form the great bulk of the low country, cannot but soon arrive at the conviction that Nature probably gave to Ireland with a liberal hand, but has again taken away what she had given. The isolated little coalfields which exist at present are but the remnants of important deposits which have been torn away by denudation; and as they are unmistakably the few lowermost beds of the formation, no discoveries are to be expected from boring. It is, nevertheless, noticeable that the lower portions of the carboniferous strata are developed, in great thickness, for the limestone is succeeded by several hundred feet

of black shale, as in Derbyshire, and then by some 500 to 700 feet of flagstones, which form a parallel to our millstone grit. The coal measures attaining sometimes a thickness of 1,800 feet, contain but a few seams, mostly very thin, of anthracite, extremely broken, compressed, and uncertain, in county Cork, but in the Tipperary and Castlecomer fields, forming basins of considerable regularity.

In the north of Ireland, coalfields of very small extent occur in Tyrone and Antrim; which, although some of the seams are of bituminous quality, exhibit in the main characters very similar to those of the south. And thus the whole of the deposits of fossil fuel, being but fragments capable of a very limited supply, it is fortunate that the town populations of Ireland can be supplied with such facility from the Clyde, Whitehaven, the Mersey, and the Dee; and that Nature has in some measure made amends for the absence of coal by the gift of peat bogs of unsurpassed extent and quality.

CHAPTER VII.

CONTINENTAL EUROPEAN COALFIELDS.

FRANCE.-Although unable fully to supply the demands of a large population and high civilisation, the French coalfields are neither few nor poor in contents. The sum total of the coal production of France is obtained from above fifty different patches of the coal formation, only a few of which need to be cited as of permanent importance. They may be grouped as the

coalfields of the north, of the centre, and of the south.

That of the north, occupying a narrow strip of land in the departments du Nord and Pas de Calais, is at the one end continuous with that of Belgium, whilst on the other it gradually diminishes in value as it is followed from Valenciennes and Bethune, towards Hardinghen and Boulogne. Considering how the coal、 measures are covered by the chalk, or cretaceous strata, 80 to 150 yards thick, some of them offering very serious obstacles to the sinking of shafts, it is creditable to the sagacity and perseverance of the French engineers and coal owners that they have so ferreted out the character and position of these concealed treasures, as to have brought the production of this field already up to three millions of tons. The seams are not actually traceable without a gap into Belgium, but are of a similar character,-regular and numerous, yet thin thus the 12 beds of Aniche give together but 23 feet of coal; 4 beds worked at Douchy, 11 feet 6 inches; 18 at Anzin, 39 feet.

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A comparison of these features with those exhibited on the flanks of our Mendip hills, and an observation of the underground course of the sharp trough of French coal strata, deflected as it is from its Belgian direction when it arrives at Douay, inclines us to the speculation that the palæozoic rocks may be continuous from the Severn to the Rhine. The question may possibly be of little practical importance, but is one of great interest as regards the original deposition of the carboniferous series.*

* Mr. Godwin Austin long since propounded this view on purely geological grounds. Quart. Jour. Geol. Soc., vol. xi.

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The coalfields of central France are remarkable for their irregular and small area, and the fragmentary and unequal state in which most of the seams occur. They are commonly based upon some of the primary rocks, granite, gneiss, &c.; and a great part of their constituent mass consists of coarse grits, and, towards the base, of rough conglomerate. The seams attain, here and there, a vast thickness, even up to 40, 60, and 80 feet, but are much broken, and subject to sudden changes. Some of the French geologists are inclined to consider them the result of deposition in lakes, in contradistinction to the fields of the North and of England, where they repose in the obviously marine beds of the mountain limestone.

The most important of them is the district of St. Etienne and Rive de Gier (Loire), occupying a length of about 34 miles, and in which the lower seams occupy an area of 60,000 acres. One of these varies from 30 to 70 feet in thickness. On these follow some hundreds of yards thick of barren sandstones, and then an upper series of 20 seams of from 3 to 16 feet thick, which only cover a surface of about 10,000 acres, and in the midst of which the full thickness of the basin appears to be near 5,000 feet. The active manufacturing industry of this neighbourhood has raised the production to as much as three millions of tons.

Another remarkable basin is that of the Saône et Loire, the chief working centres of which are Creusot, Blanzy, Montceau, Montchanin, and Epignac, where the measures contain only ten beds of coal, but at Blanzy two of them run from 30 to 60 feet each; and at Montchanin, as at Creusot, one seam attains locally the extraordinary amount of from 60 to 130 feet in thickness.

Most of these central fields are, unfortunately, mere basins in the older rocks, so that their contents are rigidly defined; yet a few of them-as that of Creusot and Blanzy-offer some prospect of continuation, especially on the south-west, beneath the covering of newer formations.

In the south, the coalfield of Alais, in the departments du Gard and Ardeche, conveniently situate for the supply of the coasts of the Mediterranean, and that of the Aveyron, are both of them noticeable for a yield which has increased much within a few years past, and for having probable reserves beneath the jurassic strata, which on certain sides bound the visible extent of the coal-measures.

In 1863, with a home production of 10 millions of tons-increased in 1869 to 13,000,000-France consumed half as much again imported from abroad.* Since 1815 the amount raised from French pits has been multiplied tenfold; but it is still a problem whether the rapidly increasing demand will ever be met by the production of the country. My own visits to a few pits have impressed on me the conviction that the French coal-seams are usually much more difficult to work economically than our own; and that hence the prices, ruling higher than in more favoured districts, will always render it difficult for the coal-owners to compete on the large scale with those of England, Belgium, or Prussia.

BELGIUM.—The deepest pits in the world have been opened in that narrow, but actively worked, zone of

* The imports into France were, in 1864:

6,500,000 tons.