As compared with some of the American coal-fields, those of Britain are but small, both in extent and thickness. They can be regarded as falling naturally into three principal areas.
The northern coal-field, including those of Fife, Stirling, and Ayr
in Scotland; Cumberland, Newcastle, and Durham in England; Tyrone
in Ireland.
The middle coal-field, all geologically in union, including those of
Yorkshire, Derbyshire, Shropshire, Staffordshire, Flint, and
Denbigh.
The southern coal-field, including South Wales, Forest of Dean,
Bristol, Dover, with an offshoot at Leinster, &c., and Millstreet,
Cork.
Thus it will be seen that while England and Scotland are, in comparison with their extent of surface, bountifully supplied with coal-areas, in the sister island of Ireland coal-producing areas are almost absent. The isolated beds in Cork and Tipperary, in Tyrone and Antrim, are but the remnants left of what were formerly beds of coal extending the whole breadth and length of Ireland. Such beds as there remain undoubtedly belong to the base of the coal-measures, and observations all go to show that the surface suffered such extreme denudation subsequent to the growth of the coal-forests, that the wealth which once lay there, has been swept away from the surface which formerly boasted of it.
On the continent of Europe the coal-fields, though not occupying so large a proportion of the surface of the country as in England, are very far from being slight or to be disregarded. The extent of forest-lands still remaining in Germany and Austria are sufficing for the immediate needs of the districts where some of the best seams occur. It is only where there is a dearth of handy fuel, ready to be had, perhaps, by the simple felling of a few trees, that man commences to dig into the earth for his fuel. But although on the continent not yet occupying so prominent a position in public estimation as do coal-fields in Great Britain, those of the former have one conspicuous characteristic, viz., the great thickness of some of the individual seams.
In the coal-field of Midlothian the seams of coal vary from 2 feet to 5 feet in thickness. One of them is known as the "great seam," and in spite of its name attains a thickness only of from 8 to 10 feet thick. There are altogether about thirty seams of coal. When, however, we pass to the continent, we find many instances, such as that of the coal-field of Central France, in which the seams attain vast thicknesses, many of them actually reaching 40 and 60 feet, and sometimes even 80 feet. One of the seams in the district of St. Etienne varies from 30 to 70 feet thick, whilst the fifteen to eighteen workable seams give a thickness of 112 feet, although the total area of the field is not great. Again, in the remarkable basin of the Saône-et-Loire, although there are but ten beds of coal, two of them run from 30 to 60 feet each, whilst at Creusot the main seam actually runs locally to a thickness varying between 40 and 130 feet.
The Belgian coal-field stretches in the form of a narrow strip from 7 to 9 miles wide by about 100 miles long, and is divided into three principal basins. In that stretching from Liége to Verviers there are eighty-three seams of coal, none of which are less than 3 feet thick. In the basin of the Sambre, stretching from Namur to Charleroi, there are seventy-three seams which are workable, whilst in that between Mons and Thulin there are no less than one hundred and fifty-seven seams. The measures here are so folded in zigzag fashion, that in boring in the neighbourhood of Mons to a depth of 350 yards vertical, a single seam was passed through no less than six times.
Germany, on the west side of the Rhine, is exceptionally fortunate in the possession of the famous Pfalz-Saarbrücken coal-field, measuring about 60 miles long by 20 miles wide, and covering about 175 square miles. Much of the coal which lies deep in these coal-measures will always remain unattainable, owing to the enormous thickness of the strata, but a careful computation made of the coal which can be worked, gives an estimate of no less than 2750 millions of tons. There is a grand total of two hundred and forty-four seams, although about half of them are unworkable.
Beside other smaller coal-producing areas in Germany, the coal-fields of Silesia in the southeastern corner of Prussia are a possession unrivalled both on account of their extent and thickness. It is stated that there exist 333 feet of coal, all the seams of which exceed 2-1/2 feet, and that in the aggregate there is here, within a workable depth, the scarcely conceivable quantity of 50,000 million tons of coal.
The coal-field of Upper Silesia, occupying an area about 20 miles long by 15 miles broad, is estimated to contain some 10,000 feet of strata, with 333 feet of good coal. This is about three times the thickness contained in the South Wales coal-field, in a similar thickness of coal-measures. There are single seams up to 60 feet thick, but much of the coal is covered by more recent rocks of New Red and Cretaceous age. In Lower Silesia there are numerous seams 3-1/2 feet to 5 feet thick, but owing to their liability to change in character even in the same seam, their value is inferior to the coals of Upper Silesia.
When British supplies are at length exhausted, we may anticipate that some of the earliest coals to be imported, should coal then be needed, will reach Britain from the upper waters of the Oder.
The coal-field of Westphalia has lately come into prominence in connection with the search which has been made for coal in Kent and Surrey, the strata which are mined at Dortmund being thought to be continuous from the Bristol coal-field. Borings have been made through the chalk of the district north of the Westphalian coal-field, and these have shown the existence of further coal-measures. The coal-field extends between Essen and Dortmund a distance of 30 miles east and west, and exhibits a series of about one hundred and thirty seams, with an aggregate of 300 feet of coal.
It is estimated that this coal-field alone contains no less than 39,200 millions of tons of coal.
Russia possesses supplies of coal whose influence has scarcely yet been felt, owing to the sparseness of the population and the abundance of forest. Carboniferous rocks abut against the flanks of the Ural Mountains, along the sides of which they extend for a length of about a thousand miles, with inter-stratifications of coal. Their actual contents have not yet been gauged, but there is every reason to believe that those coal-beds which have been seen are but samples of many others which will, when properly worked, satisfy the needs of a much larger population than the country now possesses.
Like the lower coals of Scotland, the Russian coals are found in the carboniferous limestone. This may also be said of the coal-fields in the governments of Tula and Kaluga, and of those important coal-bearing strata near the river Donetz, stretching to the northern corner of the Sea of Azov. In the last-named, the seams are spread over an area of 11,000 square miles, in which there are forty-four workable seams containing 114 feet of coal. The thickest of known Russian coals occur at Lithwinsk, where three seams are worked, each measuring 30 feet to 40 feet thick.
An extension of the Upper Silesian coal-field appears in Russian Poland. This is of upper Carboniferous age, and contains an aggregate of 60 feet of coal.
At Ostrau, in Upper Silesia (Austria), there is a remarkable coal-field. Of its 370 seams there are no less than 117 workable ones, and these contain 350 feet of coal. The coals here are very full of gas, which even percolates to the cellars of houses in the town. A bore hole which was sunk in 1852 to a depth of 150 feet, gave off a stream of gas, which ignited, and burnt for many years with a flame some feet long.
The Zwickau coal-field in Saxony is one of the most important in Europe. It contains a remarkable seam of coal, known as Russokohle or soot-coal, running at times 25 feet thick. It was separated by Geinitz and others into four zones, according to their vegetable contents, viz.:—
2. Zone of Annularia and Calamites.
4. Zone of Sagenaria (in Silesia), equivalent to the culm-measures of Devonshire.
Coals belonging to other than true Carboniferous age are found in Europe at Steyerdorf on the Danube, where there are a few seams of good coal in strata of Liassic age, and in Hungary and Styria, where there are tertiary coals which approach closely to those of true Carboniferous age in composition and quality.
In Spain there are a few small scattered basins. Coal is found overlying the carboniferous limestone of the Cantabrian chain, the seams being from 5 feet to 8 feet thick. In the Satero valley, near Sotillo, is a single seam measuring from 60 feet to 100 feet thick. Coal of Neocomian age appears at Montalban.
When we look outside the continent of Europe, we may well be astonished at the bountiful manner in which nature has laid out beds of coal upon these ancient surfaces of our globe.
Professor Rogers estimated that, in the United States of America, the coal-fields occupy an area of no less than 196,850 square miles.
Here, again, it is extremely probable that the coal-fields which remain, in spite of their gigantic existing areas, are but the remnants of one tremendous area of deposit, bounded only on the east by the Atlantic, and on the west by a line running from the great lakes to the frontiers of Mexico. The whole area has been subjected to forces which have produced foldings and flexures in the Carboniferous strata after deposition. These undulations are greatest near the Alleghanies, and between these mountains and the Atlantic, whilst the flexures gradually dying out westward, cause the strata there to remain fairly horizontal. In the troughs of the foldings thus formed the coal-measures rest, those portions which had been thrown up as anticlines having suffered loss by denudation. Where the foldings are greatest there the coal has been naturally most altered; bituminous and caking-coals are characteristic of the broad flat areas west of the mountains, whilst, where the contortions are greatest, the coal becomes a pure anthracite.
It must not be thought that in this huge area the coal is all uniformly good. It varies greatly in quality, and in some districts it occurs in such thin seams as to be worthless, except as fuel for consumption by the actual coal-getters. There are, too, areas of many square miles in extent, where there are now no coals at all, the formation having been denuded right down to the palaeozoic back-bone of the country.
Amongst the actual coal-fields, that of Pennsylvania stands pre-eminent. The anthracite here is in inexhaustible quantity, its output exceeding that of the ordinary bituminous coal. The great field of which this is a portion, extends in an unbroken length for 875 miles N.E. and S.W., and includes the basins of Ohio, Maryland, Virginia, Kentucky, and Tennessee. The workable seams of anthracite about Pottsville measure in the aggregate from 70 to 207 feet. Some of the lower seams individually attain an exceptional thickness, that at Lehigh Summit mine containing a seam, or rather a bed, of 30 feet of good coal.
A remarkable seam of coal has given the town of Pittsburg its name. This is 8 feet thick at its outcrop near the town, and although its thickness varies considerably, Professor Rogers estimates that the sheet of coal measures superficially about 14,000 square miles. What a forest there must have existed to produce so widespread a bed! Even as it is, it has at a former epoch suffered great denudation, if certain detached basins should be considered as indicating its former extent.
The principal seam in the anthracite district of central Pennsylvania, which extends for about 650 miles along the left bank of the Susquehanna, is known as the "Mammoth" vein, and is 29-1/2 feet thick at Wilkesbarre, whilst at other places it attains to, and even exceeds, 60 feet.
On the west of the chain of mountains the foldings become gentler, and the coal assumes an almost horizontal position. In passing through Ohio we find a saddle-back ridge or anticline of more ancient strata than the coal, and in consequence of this, we have a physical boundary placed upon the coal-fields on each side.
Passing across this older ridge of denuded Silurian and other rocks, we reach the famous Illinois and Indiana coal-field, whose coal-measures lie in a broad trough, bounded on the west by the uprising of the carboniferous limestone of the upper Mississippi. This limestone formation appears here for the first time, having been absent on the eastern side of the Ohio anticline. The area of the coal-field is estimated at 51,000 square miles.
In connection with the coal-fields of the United States, it is interesting to notice that a wide area in Texas, estimated at 3000 square miles, produces a large amount of coal annually from strata of the Liassic age. Another important area of production in eastern Virginia contains coal referable to the Jurassic age, and is similar in fossil contents to the Jurassic of Whitby and Brora. The main seam in eastern Virginia boasts a thickness of from 30 to 40 feet of good coal.
Very serviceable lignites of Cretaceous age are found on the Pacific slope, to which age those of Vancouver's Island and Saskatchewan River are referable.
Other coal-fields of less importance are found between Lakes Huron and
Erie, where the measures cover an area of 5000 square miles, and also in
Rhode Island.
In British North America we find extensive deposits of valuable coal-measures. Large developments occur in New Brunswick and Nova Scotia. At South Joggins there is a thickness of 14,750 feet of strata, in which are found seventy-six coal-seams of 45 feet in total thickness. At Picton there are six seams with a total of 80 feet of coal. In the lower carboniferous group is found the peculiar asphaltic coal of the Albert mine in New Brunswick. Extensive deposits of lignite are met with both in the Dominion and in the United States, whilst true coal-measures flank both sides of the Rocky Mountains. Coal-seams are often encountered in the Arctic archipelago.
The principal areas of deposit in South America are in Brazil, Uruguay, and Peru. The largest is the Candiota coal-field, in Brazil, where sections in the valley of the Candiota River show five good seams with a total of 65 feet of coal. It is, however, worked but little, the principal workings being at San Jeronimo on the Jacahahay River.
In Peru the true carboniferous coal-seams are found on the higher ground of the Andes, whilst coal of secondary age is found in considerable quantities on the rise towards the mountains. At Porton, east of Truxillo, the same metamorphism which has changed the ridge of sandstone to a hard quartzite has also changed the ordinary bituminous coal into an anthracite, which is here vertical in position. The coals of Peru usually rise to more than 10,000 feet above the sea, and they are practically inaccessible.
Cretaceous coals have been found at Lota in Chili, and at Sandy Point,
Straits of Magellan.
Turning to Asia, we find that coal has been worked from time to time at
Heraclea in Asia Minor. Lignites are met with at Smyrna and Lebanon.
The coal-fields of Hindoostan are small but numerous, being found in all parts of the peninsula. There is an important coal-field at Raniganj, near the Hooghly, 140 miles north of Calcutta. It has an area of 500 square miles. In the Raniganj district there are occasional seams 20 feet to 80 feet in thickness, but the coals are of somewhat inferior quality.
The best quality amongst Indian coals has come from a small coal-field of about 11 square miles in extent, situated at Kurhurbali on the East Indian Railway. Other coal-fields are found at Jherria and on the Sone River, in Bengal, and at Mopani on the Nerbudda. Much is expected in future from the large coal-field of the Wardha and Chanda districts, in the Central Provinces, the coal of which may eventually prove to be of Permian age.
The coal-deposits of China are undoubtedly of tremendous extent, although from want of exploration it is difficult to form any satisfactory estimate of them. Near Pekin there are beds of coal 95 feet thick, which afford ample provision for the needs of the city. In the mountainous districts of western China the area over which carboniferous strata are exposed has been estimated at 100,000 square miles. The coal-measures extend westward to the Mongolian frontier, where coal-seams 30 feet thick are known to lie in horizontal plane for 200 miles. Most of the Chinese coal-deposits are rendered of small value, either owing to the mountainous nature of the valleys in which they outcrop, or to their inaccessibility from the sea. Japan is not lacking in good supplies of coal. A colliery is worked by the government on the island of Takasima, near Nagasaki, for the supply of coals for the use of the navy.
The British possession of Labuan, off the island of Borneo, is rich in a coal of tertiary age, remarkable for the quantity of fossil resin which, it contains. Coal is also found in Sumatra, and in the Malayan Archipelago.
In Cape Colony and Natal the coal-bearing Karoo beds are probably of New
Red age. The coal is reported to be excellent in quantity.
In Abyssinia lignites are frequently met with in the high lands of the interior.
Coal is very extensively developed throughout Australasia. In New South Wales, coal-measures occur in large detached portions between 29° and 35° S. latitude. The Newcastle district, at the mouth of the Hunter river, is the chief seat of the coal trade, and the seams are here found up to 30 feet thick. Coal-bearing strata are found at Bowen River, in Queensland, covering an area of 24,000 square miles, whilst important mines of Cretaceous age are worked at Ipswich, near Brisbane. In New Zealand quantities of lignite, described as a hydrous coal, are found and utilised; also an anhydrous coal which may prove to be either of Cretaceous or Jurassic age.
We have thus briefly sketched the supplies of coal, so far as they are known, which are to be found in various countries. But England has of late years been concerned as to the possible failure of her home supplies in the not very distant future, and the effects which such failure would be likely to produce on the commercial prosperity of the country.
Great Britain has long been the centre of the universe in the supply of the world's coal, and as a matter of fact, has been for many years raising considerably more than one half of the total amount of coal raised throughout the whole world. There is, as we have seen, an abundance of coal elsewhere, which will, in the course of time, compete with her when properly worked, but Britain seems to have early taken the lead in the production of coal, and to have become the great universal coal distributor. Those who have misgivings as to what will happen when her coal is exhausted, receive little comfort from the fact that in North America, in Prussia, in China and elsewhere, there are tremendous supplies of coal as yet untouched, although a certain sense of relief is experienced when that fact becomes generally known.
If by the time of exhaustion of the home mines Britain is still dependent upon coal for fuel, which, in this age of electricity, scarcely seems probable, her trade and commerce will feel with tremendous effect the blow which her prestige will experience when the first vessel, laden with foreign coal, weighs anchor in a British harbour. In the great coal lock-out of 1893, when, for the greater part of sixteen weeks scarcely a ton of coal reached the surface in some of her principal coal-fields, it was rumoured, falsely as it appeared, that a collier from America had indeed reached those shores, and the importance which attached to the supposed event was shown by the anxious references to it in the public press, where the truth or otherwise of the alarm was actively discussed. Should such a thing at any time actually come to pass, it will indeed be a retribution to those who have for years been squandering their inheritance in many a wasteful manner of coal-consumption.
Thirty years ago, when so much small coal was wasted and wantonly consumed in order to dispose of it in the easiest manner possible at the pitmouths, and when only the best and largest coal was deemed to be of any value, louder and louder did scientific men speak in protest against this great and increasing prodigality. Wild estimates were set on foot showing how that, sooner or later, there would be in Britain no native supply of coal at all, and finally a Royal Commission was appointed in 1866, to collect evidence and report upon the probable time during which the supplies of Great Britain would last.
This Commission reported in 1871, and the outcome of it was that a period of twelve hundred and seventy-three years was assigned as the period during which the coal would last, at the then-existing rate of consumption. The quantity of workable coal within a depth of 4000 feet was estimated to be 90,207 millions of tons, or, including that at greater depths, 146,480 millions of tons. Since that date, however, there has been a steady annual increase in the amount of coal consumed, and subsequent estimates go to show that the supplies cannot last for more than 250 years, or, taking into consideration a possible decrease in consumption, 350 years. Most of the coal-mines will, indeed, have been worked out in less than a hundred years hence, and then, perhaps, the competition brought about by the demand for, and the scarcity of, coal from the remaining mines, will have resulted in the dreaded importation of coal from abroad.
In referring to the outcome of the Royal Commission of 1866, although the Commissioners fixed so comparatively short a period as the probable duration of the coal supplies, it is but fair that it should be stated that other estimates have been made which have materially differed from their estimate. Whereas one estimate more than doubled that of the Royal Commission, that of Sir William Armstrong in 1863 gave it as 212 years, and Professor Jevons, speaking in 1875 concerning Armstrong's estimate, observed that the annual increase in the amount used, which was allowed for in the estimate, had so greatly itself increased, that the 212 years must be considerably reduced.
One can scarcely thoroughly appreciate the enormous quantity of coal that is brought to the surface annually, and the only wonder is that there are any supplies left at all. The Great Pyramid which is said by Herodotus to have been twenty years in building, and which took 100,000 men to build, contains 3,394,307 cubic yards of stone. The coal raised in 1892 would make a pyramid which would contain 181,500,000 cubic yards, at the low estimate that one ton could be squeezed into one cubic yard.
The increase in the quantity of coal which has been raised in succeeding years can well be seen from the following facts.
In 1820 there were raised in Great Britain about 20 millions of tons. By 1855 this amount had increased to 64-1/2 millions. In 1865 this again had increased to 98 millions, whilst twenty years after, viz., in 1885, this had increased to no less than 159 millions, such were the giant strides which the increase in consumption made.
In the return for 1892, this amount had farther increased to 181-1/2 millions of tons, an advance in eight years of a quantity more than equal to the total raised in 1820, and in 1894 the total reached 199-1/2 millions; this was produced by 795,240 persons, employed in and about the mines.