THE COAI-FIELDS OF GREAT BRITAIN. *
Ir was the belief of the late Dr. Buckland that the supply yielded by our coal-fields would be sensibly diminished in no very distant
• The Coal-fields of Great Britain: their History, Structure, and Duration. With Notices of the Coal-fields of other Parts of the World. By Edward Hufl, BA., of the Geological Survey of Great Britain. With Illustrations. Published by Stanford.
future. Mr. 'Vivian holds that they are, practically speaking, inexhaustible, and the Government and the Legislature have re- cently based their proceedings upon the same view of the ques- tion. Such, however, was the extreme diversity of opinions ex- pressed upon the point during the debates on the Commercial Treaty with France as to throw doubts upon the authenticity of all the data on which those discordant opinions were respectively founded. Now, it is surely of the highest importance that the public should know accurately whether or not this country can, without irre- trievable damage to its resources, admit of the unrestrained ex- port of coal ; and, therefore, Mr. Hull could not have more use- fully employed his talents, and the unrivalled resources at his command, than in taking stock of the great deposits of mineral wealth on which we are drawing so largely, and at so rapidly- increasing a rate. The conclusion he has come to is, prim& facie, encouraging. He finds that, adopting a depth of 4000 feet as the limit to deep mining, there is still a quantity of coal in store in England and Wales, sufficient to afford a supply of sixty millions of tons (not quite 5 per cent more than the present consumption) for about a thousand years.
Mr. Hull's method of proceeding has been to examine each coal- field separately, ascertain its area, the total quantity of coal within it, the proportion of this which is workable, the deduction to be made for waste and for what has been already extracted, and the net quantity which remains for future supply. He begins the statistical portion of his work with the South Wales coal- field, the largest in England, and containing a greater vertical thickness of strata than any in the world, with the exception of that of Nova Scotia. " When," he says, " we regard the enormous amount of fuel which is stored up throughout a thick- ness of strata (10,000 feet) out of which might be cut a mountain about three times the height of Snowdon, having a basis of a thousand square miles ; and which, as Mr. Vivian has shown, could supply the whole consumption of Britain for nearly 5000 years, it seems almost profane to assert that at least one-half of this store must lie for ever beyond our reach, and thus, as far as man is concerned, to have been made for naught. If, therefore, there are those who consider 4000 feet as too narrow a limit, it will be satisfactory to them to be assured that they have here a store of fuel well nigh limitless, and which if it had been drawn upon to its present extent since the days of the Noachian deluge, would even still be unexhansted." The average annual produce of this great coal basin is eight millions of tons, but if opened up to an extent proportional to that of Yorkshire, it ought to yield thirteen millions of tons annually. In estimating its available mineral resources, Mr. Hull leaves out of the account all coal- seams of less than two feet thickness, as not capable of being worked with profit. There then remains a total quantity of coal (corrected for denudation), amounting to 48,000 millions of tons. Mr. Vivian, who makes the quantity somewhat greater, regards the whole of it as available, and sees in it a source of con- stant supply for 6000 years, at the present rate of consumption. Mr. Hull, on the other hand, cuts off at one stroke a full half from his gross estimate, on account of the quantity lying below 4000 feet from the surface ; and, from the remaining half, he deducts one-ihird for waste and quantity already extracted. This leaves for future supply 16,000 millions of tons, enough for 2000 years at the present average annual produce ; but this, as before remarked, is capable of being greatly increased. The Derby and Yorkshire coal-field, which extends also into Not- tinghamshire, is the largest in England, and its area is only 150 square miles less than that of the South Wales field. It supports 541 collieries, which produced 121- millions of tons in 1857, and is estimated by Mr. Hull to have 21,000 millions remaining for future use. The Great Northern coal-field of Northumberland and Durham contains 288 collieries, the produce of which was, in 1857, nearly 16 millions of tons, and has been increasing ever since. This field will last, according to Mr. Hull's calculation, for 466 years at the present rate'of consumption ; its remaining avail- able stock being 7432 millions. This is somewhat more than the quantity assigned in the estimates of some eminent local authori- ties. Mr. Hugh Taylor, now M.P. for Tynemouth, in his evidence before a Select Committee of the House of Lords in 1829, esti- mated the duration of the Northern coal-field at 1727 years, the annual consumption being then 3i millions of tons. He appears, therefore, to have reckoned the quantity of unworked coal at about 6000 millions of tons. It was set down at 5121 millions by Mr. T. Y. Hall in 1854, and the duration of the field at 365 years, supposing the consumption not to exceed what was then the annual rate, namely, 14 millions of tons. In consequence, how- ever, of the great annual increase in the demand for coal from this field, Mr. Hull assumed that the annual consumption was not unlikely, before many years, to reach 20 millions. At that rate, the coal-field would be exhausted in the course of 256 years.
In all the seventeen coal-fields of England and Wales, the total available quantity of coal within a depth of 4000 feet is 59,109 millions of tons. In calculating that this supply will last for about a thousand years, Mr. Hull counts upon an annual con- sumption not exceeding 60 millions of tons, the actual consump- tion being 57 millions. If these results, he says, " can only be regarded as approximately accurate—and, considering the nature of the inquiry they can scarcely pretend to more—they are at least sufficient to show that for many generations to come the mineral resources of England are capable of bearing any drain to which they can possibly be subjected either for home or foreign consump- tion." These are very encouraging words ; and yet, with all our defer- ence to Mr. Hull's authority, and our desire that his comforting conclusions may be well founded, we cannot quite overcome our
misgivings. It appears to us that, in assuming only 60 millions of tons as the annual produce of the English and Welsh collieries
to the end of their duration, he has allowed much too narrow a margin—only 3 millions—for the increase of future years. In thirty years, between 1829 and 1859, the produce of the great Northern• field increased nearly tive-fold. With a much wider
market now opened, and in the infancy of a demand, the ultimate magnitude of which cannot now be measured, what is there to
show that the aggregate produce of all our coal-fields may not las:- wise be quintupled in thirty years, or even within a much shorter period ? This is not a geological question, nor one as to which Mr. Hull can be supposed to possess any extraordinary in- sight. It is a question upon which no man's dictum can be ac- cepted, however great his commercial knowledge, for many examples testify how nugatory is the attempt to foretell the maxi- mum extent to which any great branch of traffic ma ..ssibly be developed under new and favourable conditions. , at if the seemingly remote catastrophe of exhaustion were to quicken its pace, and arrive in 250, or 200, or 150 years ? If that were all, even that would be a sufficiently painful prospect ; but, long be-
fore the final disaster, its approach would be indicated by many a bitter foretaste of the evils incident to the extinction of a vast department of national industry. To escape, if possible, from the apprehension of this deplorable contingency, let us see why it is we are forbidden to put our trust in Mr. Vivian, who encourages us to hope that the immense deposits of coal below the depth of 4000 feet are not absolutely beyond our reach. It must be owned that Mr. Hull's reasons for holding the con- trary opinion are weighty indeed ; but as yet they are in a great measure only speculative, the means of fully testing them by ex- perience being absent ; for the deepest coal-mine in England, that of Dukinfield, Cheshire, has a depth of but 2055 feet. Now it is known that the temperature of the earth increases progressively from the surface downwards, and the result of many observations gives one degree of Fahrenheit as the average rate of increase for every sixty feet. This is the actual rate of increase in the Monk- wearmouth colliery ; in some of the mines of Cornwall, and in some artesian wells, the increase is more rapid ; but in Dukinfield colliery the rate is not uniform, and its average for the whole depth is 1° for every 83.2 feet. " It is not easy," says Mr. Hull, " to account for the less rapid increase of temperature, as shown by these experiieents, than that determined by a large number from other sources. It may possibly happen that the coal forma- tion, formed as it is of a great variety of strata differing in den- sity and conducting power, may present greater obstacles to the upward extension of subterranean heat than formations of more uniform texture." There is much solace in this suggestion. " But," he continues, " whatever may be the cause, the above results justify us in assuming a more gradual increase than one degree for 60 feet, in the case of coal-mines ; and, if we adopt an amount of one degree for 70 feet, which is a mean value between the results obtained at Dukinfield colliery and other sources, we shall not greatly err." At 50 feet underground, the temperature is constant at 50° 5' F. Taking this, then, as the standard of de- parture, and adding to it one degree for every 70 feet as the in- crease due to depth, and one degree in every 300 feet as that due to the augmented density of the air, Mr. null arrives at 91° as the resulting theoretical temperature at the depth of 2500 feet, and 120° at 4000. Hence he infers that, were there no compen- sating agencies, a depth of about 2500 feet would be the limit to deep mining, as it would not be possible for our miners to work at a higher temperature than 94°, which is almost that of the tropics. Good ventilation, however, is very potent in cooling mines ; and he believes that, in winter, and in that season only, when the air at the surface is from 30° to 40°, it will be quite possible to reduce the heat, even of a mine 4000 feet in depth, to a degree not only tolerable, but admitting of healthy labour. Beyond that depth, he does not believe it will be practicable to penetrate. This reasoning looks vexatiously strong. Will Mr. Vivian or anybody else oblige us by picking a hole in it? If this cannot be done, we must be content to await the result of further expe- rience, which may peradventure supersede the data upon which Mr. Hull has based his argument. We have lived to see many things done, the impossibility of which had been scientifically demonstrated.
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