Yet, in spite of all the interdictions, complaints, and prejudices arrayed against it, coal continued to grow in use; for as early as 1615, Newcastle gave employment to about four hundred vessels, one-half of which number supplied the demands of London. French ships even then fetched coals in that port, and the Hanse towns conveyed them to Flanders.
About the middle of the seventeenth century the coal trade, notwithstanding an increase of price, required nine hundred vessels; and fifty years later, half a million of tons were exported from Newcastle, requiring fourteen hundred vessels for their carriage. During the eighteenth century the northern coal trade constantly increased with the steady growth of London, which in 1770, although not possessing one-sixth of its present population, already consumed seven hundred thousand tons; and it would have been impossible for the collieries to satisfy the constantly growing demand if the invention of the steam-engine had not lent its powerful aid to raise larger quantities of coal from a greater depth, and to drain many works which otherwise would have been deluged with water.
The other English coal-fields began to be worked at a much later period than that of Newcastle, but rapidly grew in importance with the vast increase of our manufactories and smelting furnaces.
The extraction of coal is indeed constantly increasing at a truly gigantic rate. Thus, in 1845 our whole annual production was rated at thirty-five millions of tons; in 1859 it amounted, according to trustworthy returns, to sixty-eight millions; in 1865 it had advanced to ninety-six million tons; and now probably exceeds one hundred million tons—a mass so enormous that with it a girdle of coal three feet wide, and about seven high, might be put round the earth.
The question of the duration of our coal-fields is evidently one of great national interest. It has of late excited the attention both of statesmen and philosophers, but unfortunately it is more easily put than answered. While some authorities give us the cheering assurance that we have enough to last us for the next two thousand years at least, others limit our supply to three or four centuries, or assign even a couple of hundred years as the period when our descendants will have to seek their coals in the mines of other countries. The quantity of fuel left in the Newcastle basin—the most anciently worked of our coal-fields—was estimated by Mr. Hall, in 1854, at 5,121,888,956 tons. Dividing this total by 20,000,000 of tons as the present annual consumption, the future supplies of this famous coal-field would thus be limited to about two hundred and fifty years—a very short period in the history of a nation. The immense consumption of coal in the iron furnaces and foundries of Staffordshire will probably lead to an exhaustion of that coal-field even before Northumberland and Durham, for its area is scarcely more than one-half of the area of the Northern Coal-field. It has, indeed, one very thick seam of coal of from thirty to forty feet, but this will not alone compensate the difference. The coal-fields of Yorkshire, Lancashire, and Derbyshire, situated amongst the numerous iron-works and manufactories, as well as large populations, justify a similar prophecy; but, on the other hand, better prospects are held out by the great coal-field of South Wales.
After deducting the coal practically unattainable from its depth, sixty thousand millions of tons may be considered a liberal estimate of the available mass. At the present rate of extraction (ten millions of tons) this would give a supply for the next six thousand years; but supposing the other sources to fail, the extraction of coal from the South Wales basin would of course be increased to such an extent as to limit its duration to six or seven centuries. It may be remarked that the largest estimates of future coal supply are based on the assumption that mines may be worked at a depth of four or five thousand feet; but this is very problematical. Mechanical skill may indeed pierce shafts to this depth, or even deeper; but the increase of temperature which is raised by one degree for about every successive seventy feet, along with the increasing density of the air, must ever oppose insuperable obstacles to human labour at such a distance below the level of the sea. To the natural heat and density arising from depth must be added the corruptions arising from human perspiration, which are constantly on the increase during working hours in working places. ‘We speak,’ says the author of an excellent article in the Quarterly Review,[[66]] ‘from some brief personal experience of what these things are at a depth of nearly eighteen hundred feet, where the actual temperature varied from eighty-five to eighty-six and a half degrees. Such experience is necessary to qualify any man to judge of the vertical limit of human labour, and we hesitate to fix it at more than two thousand five hundred feet, and should fix it at that depth only for the hardiest of hewers and haulers of coal.’
The pressure of superincumbent strata, which renders the upholding of the roof, even at fourteen or fifteen hundred feet, a problem of ceaseless anxiety and expense, must also be taken into account. At depths much exceeding two thousand feet, it is very doubtful if the roofs could be securely upheld except at such an outlay as would considerably raise the cost of extraction, while the coal itself would be more and more dense, and therefore more and more difficult to dislodge. For these various reasons, all the strata of coal situated below the depth of two thousand five hundred feet, or at the very utmost three thousand feet, may be considered as practically unworkable; and thus sober-minded calculators, on comparing the available solid contents of our coal-fields with the rate of extraction, have come to the conclusion that a thousand years is the maximum of the probable future supply of England and Wales. Adding to this the Scotch and Irish coal, which are not included in the estimate, and swelling our account with lignite and peat, we have at any rate sufficient materials for keeping our fires burning for a good time to come, and may safely leave all desponding views on the subject to distant generations.
Next to England, no European country has so rapidly increased its coal production as the German empire, where, thanks to the railroads, the consumption of mineral fuel is yearly extending over a wider range, and gradually supplanting in many localities the use of wood. The official tables inform us that in 1866, 432,594,926 cwt. of black coal, and 130,661,182 cwt. of lignite—together, about 28 million tons—were produced, a mass considerably greater than the joint production of France and Belgium, and equal to about seven twenty-fifths of the production of England. The chief coal-fields are those of Upper Silesia, of the Ruhr, of the Saar, of Waldenburg (in Lower Silesia), of Dresden and Zwickau (in Saxony), of Aachen (Aix-la-Chapelle), Ibbenburen, and Minden, which not only supply the greater part of Germany, but also yield a considerable exportation to France, Switzerland, and Holland.
The German ports on the North Sea and the Baltic still largely consume British coal, which, however, has been entirely driven from the Rhine; and Berlin, which in 1860 burnt 202,970 tons of English coal, consumed little more than one-half that quantity (123,401 tons) in 1865, in spite of a considerable increase of population; while at the same time the consumption of coal from Upper Silesia increased from 61,700 to 323,712 tons.
The small but thriving kingdom of Belgium, where the collieries of Liège, Namur, and Hainaut give rise to a commercial activity unequalled on the Continent, occupies the third rank among the coal countries of Europe, its production in 1863 having amounted to 10,500,000 tons. The provinces of Namur and Liège consume almost all the coal they produce, while Mons and Charleroi, in Hainaut, export more than three millions of tons to France.