COAL AND COAL-MINING. [The following paper by HENRY D. ROGERS, Professor of Natural History in the University of Glasgow, furnishes facts and suggestions worthy of consideration in America. -ED. HARPER'S MAG.] NEW questions can be more interesting than that of the duration of our coal-fields, on which so much of the comfort and prosperity of the world depends. Before, however, attempting to consider it, it is necessary to furnish the reader, in as succinct a manner as possible, with some well-ascertained facts regarding the quantity of coal laid up in store in the great coal-fields of Europe and America. AMERICA. The United States, with its vast surface of 3,000,000 square miles, has one square mile of coal-field to every 15 square miles of territory. Great Britain has one to every 30 of surface. To approximate more nearly to any correct estimates of the relative reserves of coal in the great coal-fields of the world, we must compare the cubic quantities they contain, deducing these from multiplying their respective areas in square miles by their respective observed or assumed depths of available coal. Thus calculated: Belgium (assuming her coal-fields to possess the high average thickness asserted, of 60 feet of coal) contains about 36,000,000,000 tons. France (with the same thickness) about 59,000,000,000. The British Islands (adopting 35 feet as the average thickness) nearly 142,500,000,000. According to Mr. Hull's estimate the total supply is 79,843,000,000. Pennsylvania (computing her average of workable coal at 25 feet) has $16,400,000,000. Whole Appalachian Coal-Field (adopting the same proportion), 1,387,500,000,000. Great Middle Coal-Field of the United States in Indiana, Illinois, and Western Kentucky (also with an average of 25 feet of coal), 1,277,500,000,000. Greatestensas, Indian Territory, and Texas, accepting 10 feet as the mean thickness of the coal, 739,000,000,000. All the productive coal-fields of North America, about 4,000,000,000,000. Coal-Field in Iowa, Missouri, Kansas. AREAS OF THE COAL-FIELDS.-NORTH AMERICA. Square Miles. 200 350 British Provinces. Newfoundland Cape Breton... Picton Cumberland.. 200 New Brunswick, 6689 (only a small part, apparently about, productive).. 836 EUROPE. Britain France.. Belgium Saarbrook coal-field. Westphalia. Bohemia Saxony Spain 1686 at the lapse of 200 or 300 years from this time. 100? It demands but little arithmetic, if we accept the unassailable statistical facts already made known, to show that such a result is inevitable. In the year 1855 the coal produced and consumed from the British collieries was reported at about 64,333,333 tons; in 1859 it amounted, we are told, to about 72,000,000 tons; in 1860 to a little more than 80,000,000 tons; and in 1861 to upward of 83,500,000 tons;* and now for the past year, 1863, just closed, the rumor is, that it will not fall short of 90,000,000 tons at the lowest estimate. Square Miles. 984 510 960 380 30 [The apparent discrepancy in the calculation of the British total supply of coal given by us in the above table, with that of Mr. E. Hull, derived from his valuable work on the Coal-Fields of Great Britain, is attributable mainly to the circumstance, that our estimate relates to the gross amount of coal originally under the surfaces of the coalfields, while his has reference to the net quantities now remaining and procurable, with allowance for waste, etc., aggregated together from his special data.] The relative superficial magnitudes of the coalfields of the countries possessing coal, will be clearly recognized if we compare them by some simple unit of measure. Let this be 100 square miles. In this case, Russia will be represented by From these indisputable statements it is apparent that while, in the first interval of four years up to 1859, the average annual ratio of increase in the coal product was just about 2,000,000 tons, this ratio has since materially augmented, being indeed, between 1860 and 1861, at the least 3,500,000 tons. In other words, we can not doubt from all the data at present accessible, that the amount of the annual increase in this first half of the present decade is not less than 3,000,000, whereas in the second half of the previous decade it did not on an average materially exceed 2,000,000 tons. These figures teach us the impressive lesson that the ratio of the augmentation is itself augmenting. But Sir William Armstrong assures us that the entire quantity of available coal existing in these islands, calculated to amount to about 80,000,000,000 tons, will, with a continued yearly increase in its consumption of 2,750,000 tons, only last 212 years.† Cordially must we thank him for enjoining it upon the people and the Government to look to it that no needless and unwise wasting of a source of wealth, and power, and happiness, so precious, and yet so far from inexhaustible, should be imprudently permitted to continue. Another very vital consideration, involving man's ability to penetrate the crust of the earth to the great depths to which the observations and calculations of miners and geologists teach us that the mineral treasures, the coal-beds, layers of iron-ore, and lodes of copper, etc., reach, is that of the globe's undeviating, inevitable increase of temperature as we descend into its bowels from the surface. No matter what the latitude, or climate, or elevation above the sealevel of the spot penetrated by the mine-shaft, the rocky crust grows warmer at the swift rate of 1° of Fahrenheit on an average for each 60 feet of progress downward. With this increment of temperature, the natural warmth at a depth of 1800 feet is 30° higher than at the sur Upon the very interesting but difficult question of the probable duration of the coal supply to Britain from her own apparently so richly stocked coal-fields, very little need here be said. The subject has been aptly handled by Mr. E. Hull in his able treatise on the British coal-fields, and has been frankly and impressively discussed by Sir William Armstrong in his late inaugural address to the British Association. Both of these most competent authorities have made obvious to every student of the subject, what we ourselves have for years past felt convinced of, and have repeatedly publicly maintained, that the total supply of coal beneath the soil of Great nal of Science," is "inclined to place the possible maxiBritain, at the present rate of growth of consump-mum of production at 100,000,000 tons," and thinks that tion, must become entirely spent or exhausted there is therefore coal enough to last for eight centuries. * See a paper read before the Society of Arts by Robert Hunt, F.R.S., Keeper of Mining Records, Government School of Mines. Sir William Armstrong's statement at Newcastle differs somewhat from this, in that he cites Mr. Hunt's statistics as showing that, "at the end of 1861, the quantity of coal raised in the United Kingdom had reached the enormous total of $6,000,000 tons." + Mr. Hull, in his recent article in the "Quarterly Jour face, or rather more than 80° of Fahrenheit; | ed air, condensed by the steam-engine stationed that is to say, the miner is called on to exert his at all collieries near the pit-mouth, and this elabest muscular force, often in a constrained pos- tic air is conveyed by slender pipes down the ture and debilitated by bad air, when the walls shaft or pit, and along the mine to the places of the mine and the atmosphere around him are where the coal is to be disturbed from its long almost as hot as the air and soil at the equator repose, and cut away from the exposed edge or in the shade. face of the seam. The compressed air is pumped by the steam-engine into a receiver at the pit-head during its otherwise idle hours, or by its surplus power while drawing up the coal, or pumping out the water, from the mine, and is condensed to a tension of 45 or 50 lbs. to the square inch. It is led at the West Ardsley Com Besides this steady rise of temperature proper to the earth's crust itself, there is an additional augmentation of warmth in all deep mines, produced by the increased density of the air. It appears to obey a constantly augmenting ratio with increase of depth, but within all ordinarily penetrated depths it averages about 1° of Fah-pany's Colliery from the receiver, in metal pipes renheit for every 300 feet of depth. At 2000 feet it amounts to 6.5°, and at 4000 to 13-16°. four and a half inches in diameter, down the shaft 80 fathoms (or 480 feet) deep, and thence Now we know that an important portion of the in pipes of a less diameter to the workings, coal in our deeper coal-basins, lies, according to tubes of one or one and a quarter inch calibre the estimates I have quoted, at depths approach- bringing it to the cylinder of the machine. This ing, and even far exceeding, 4000 feet, and this compressed air, when set free at each alternating is equivalent to an augmentation of the warmth stroke of the piston, imparts to the adjacent porto the miner of some 56° of the thermometer tions of the mine a pure, dry, cool atmosphere, due to depth, and more than 13° due to increase from a well-known law of all airs or gases, that of density in the air; that is to say, equivalent when compressed they develop heat of temperato a temperature of about 120°. This far sur-ture, and that when expanding under a relaxapasses that of any climate upon the earth's surface, and is altogether too hot and relaxing for any human being to work in. Here, then, we encounter a formidable impediment to the search after all this vast stock of deep-seated mineral wealth; and there arises a pressing question, of the greatest importance to every individual and community interested in the maintenance of cheapness and plenty in the two great essentials to our social welfare, iron and coal: can this obstruction to deep mining be obviated by the aid of human ingenuity? Until very recent days neither colliery proprietors nor mine engineers could see a way to the solution of this prodigious difficulty; but an invention, steadily maturing toward practical success for several years past, and now at last working to the entire satisfaction of all who have examined its construction and principles, gives us a sanguine promise, indeed a confident assurance, that it will achieve this blessed result, though only as one of the secondary results of its wonderful capacities. I allude to an ingenious invention lately completed in Yorkshire, and now being introduced elsewhere, for cutting coal in the collieries by machinery. tion of pressure, they quickly acquire a state of comparative coolness. We have been told, indeed, in a paper descriptive of this mechanical coal-cutter, read to the British Association at its late meeting at Newcastle, that the air issues at a temperature very little below the freezing-point. The machine is supported by a cast metal frame of great solidity and firmness, and is of a size and weight proportioned to the thickness and hardness of the bed of coal to be cut. It is constructed so as to give the blow of the pick or cutter, either by the pull or the push of the piston. The form of engine hitherto found to unite the greatest degree of convenience with efficiency in practice is that known as of the "oscillating cylinder" principle. It has the merit of combining compactness of shape with a very small amount of friction in the working parts. The whole structure rests upon wheels with flanges, which are sometimes single sometimes double as the exigencies of the work demand. It is propelled forward or backward, as required, by a wheel and screw, on a ratchet and pinion, attached to one side of the engine. On the opThis coal-cutting machine has been brought to posite side is a valve-screw, for regulating by its present high efficiency at the West Ardsley the hand the admission and escape of the air Colliery, in Yorkshire, the proprietors of which, and the stroke of the piston. The machine is William Firth, Esq., and Company, of Leeds, also, in some specimens, made self-acting, much are likewise the owners, part-patentees, improv- after the fashion of the steam-hammer. When ers, and constructors of the mechanism. The working, the man seated upon the little stool in patentees are Firth, Donnisthorpe, and Co. The the rear of it moves the ratchet screw connected engine is a large iron cylinder, with a piston with the gearing of the under-carriage, and and piston-rod working to and fro in the cylin- thereby propels the whole machine along the der, and carrying or driving a massive iron or little railway or train laid parallel to the front steel pick, which cuts the coal, working long of the coal-seam, a small distance equal to the work in any desired direction, and at a very longitudinal nip or bite of the pick, and at each material saving in waste from hewing or "kirv-swiftly-repeated blow this encroachment, of an ing." The power that gives the reciprocating inch or so, is renewed to the end of the "benk" motion to the piston and pick is highly compress- or working face. In seams of coal of a thick ness not less than three feet, the driver or miner sits on a seat slid into the end of the machine, but in thinner coal-beds he must rest kneeling on a truck running on low pulleys or rollers, and traveling in the rear of the cutting-machine. The tram-road, carrying the coal-cutter, is made of Trails fastened upon cross sleepers. This railway is of a gauge which also suits the wagons in which the detached coal is carried away from the "benks" or faces, where it has been mined; and when all the fragmentary coal is cleared away, the little railway, easily taken apart and reunited, is transplanted closer up to the face of the coal-seam, and the process of cutting by the engine is resumed. There are several distinct methods or plans of working or mining the coal-seams in our collieries. That which is best adapted for the full efficiency of the coal-cutting engine is what is technically called "long work," or some modified form of this. Messrs. Firth, Donnisthorpe, & Co. much prefer this long-wall mode of mining wherever they employ their apparatus; and we conceive that every judicious miner will admit that where the coal-bed has a good roof no other plan of working the mine can afford such grand facilities for the application of the machine. Its inventors see no difficulty in adapting it to other commonly practiced modes of mining coal. I shall not be doing this interesting invention justice if I do not advert, more explicitly than I have yet done, to the important assistance it is destined to furnish to the ventilating and cooling of all deep and over warm collieries. An approximately correct notion of its efficacy as an aid to the ventilation of the working localities in a coal-mine may be gained from the facts I have now to mention. One machine, working, we shall say, 90 blows of the pick per minute, discharges, of condensed air, about 100 cubic feet per minute, which immediately becomes 300 cubic feet of cold air at the normal density. Now an ordinary roomy colliery will employ at least five of these machines, a number productive of some 1500 cubic feet of cold air per minute. But in a very well ventilated coal-mine of medium capacity the average supply of good air to each working face is, or should be, about 2000 or 2500 cubic feet per minute. This proves that each machine is competent to supply from 12 to 15 per cent. of the ventilation, with this all-important incidental benefit, that whereas the indrawn current of air acquires in its progress a warmer temperature, and grows progressively more foul and unwholesome, the air, let off by the machine, arrives perfectly fresh, and pure, and cool, precisely at the localities where the workmen are most in need of such an atmosphere. This cooling and purifying of the air at the precise spots where good air is so indispensable magnifies this secondary function of the machine beyond the mere proportion of fresh atmosphere it contributes to the general ventilation. Observations and calculations from careful experiments indicate that, in a coal-mine having a mean temperature of say 70 degrees, the reduction in the warmth of the general mass of air will amount to about five degrees, but in the immediate vicinity of the miners the cooling action is obviously much more than this difference. Another incidental advantage, the full importance and value of which we can not overestimate, is the power this strong jet of pure cold air must exercise to dilute and chill the "fire-damp," or explosive compound of the native coal-gas and the atmospheric air, and keep it below the proportions and temperature promotive of mine explosions. The inventors are fully aware of this valuable property in their machine, and are now planning a method of projecting a portion at least of the ventilating puff of the pure cool air where it will be most efficient in counteracting the fire-damp. The writer of this has seen the machine in operation, and he can aver that he was never in a colliery where the atmosphere of the coal-seams was so pure, so cool, and so wholesome to the respiratory organs; and he asks, could a more ample, more convenient ventilation of the parts of a mine most needing it be asked for? It is easy, from this wonderful attribute of the compressed air coal-cutting apparatus, to see that we may henceforth dispel all our long-established misgivings as to the capacity of the mining art to perforate the earth's crust to almost any depths, to which we may inductively infer that the treasures of the deeper coal-fields any where descend. In a coal-seam three feet three inches thick, where 1800 tons per week are cut and withdrawn, there is a saving of 27 men at the very unwholesome and severe toil of "pick work." This amounts, we are informed, in the West Ardsley Colliery, to only about 10 per cent. of the whole number employed at the colliery, for all the . other branches remain without any commensurate reduction in the numbers of their workmen. We are rejoiced to learn, moreover, that this is a real saving of the men, for they are transferred from a very severe and dangerous form of toil to more inviting kinds of labor; transferred, in fact, from the business of a collier to that more thoughtful and freer one of a mechanic. And this is done without any reduction in the wages of the miners. Every friend of the laboring classes, every well-wisher to human progress, must rejoice at the contemplation of inventions such as this, which so obviously tend to abate the hardships of the muscular human machine, and lift him to the higher level of a mind-employing and intelligent mechanic. To estimate aright the full value of any invention like this for facilitating and cheapening the mining of our "fossil fuel," we must take into view, on the one hand, the astonishing amount of wealth which this product represents, and the large and indispensable part it plays in creating new wealth by bringing into operation a multitude of arts and industries, which but for it could not exist; and, on the other hand, the many benignant uses it fulfills in promoting hu man health and domestic comfort. The magnitude of our coal product will be recognized, and the high importance of economizing the getting it be duly appreciated, when we reflect that the past year's yield of the British coal-mines has amounted to between ninety and one hundred millions of tons, that its value on sale as lifted from the mines can not fall far short of some £50,000,000, and that the coal-trade employs, it is believed, at least 300,000 persons in working and distributing the coal alone. That this mechanical invention for cutting the coal in the mine will prove a real blessing to the miner must be obvious to every person who considers the nature of one of the chief perils which unceasingly besets the miner while at his task. By the process of "hand-kirving," or hewing a cleft back into the coal-seam in some soft layer of the bed, the miner in cutting into it, say three feet in depth from the face, must make a crevice or excavation of usually from 10 to 12 inches in width at the front, tapering narrow toward the back. Now one of the commonest and least avoidable dangers to the life and limb of the miner thus carving into a coalbed with his pick, and crouching under the face of the vast block of coal he is striving to detach, is the premature and sudden dislodgment of this great lump, weighing a ton and frequently much more, and the instantaneous slipping of the ponderous mass upon him, caused by the sloping of the artificial floor he has been making. We are informed, in fact, that as high a proportion as 20 per cent. of the lives lost in coal-mines arises from this terrific crashing of the coal upon the helpless workman as he is courageously undermining it. In striking contrast with this source of danger, attended by so much waste of precious life, is the kirving or undercutting accomplished by the machine. Mr. Samuel Firth, in his paper upon it, read at Newcastle to the British Association, assures us that the West Ardsley Machine, working in the Hetton Colliery upon a hard seam, did the "kirving" three feet deep with a groove of only three inches at the face and two inches at the back, giving an average cut of only two and a half inches high; whereas the average height of hand-kirving in the same coal-seam is about 11 inches. This saving of good coal from destruction is equal, he tells us, to ninepence per ton upon the whole yield of the coal-seam. In the West Ardsley seam the saving by the machine process of cutting amounts to one shilling per ton, on the yield of the coalbed. To get a just notion of the wonderful strength, speed, accuracy, and economy with which this beautiful piece of mechanism, the coal-cutter, does its task, one must go into one of the collieries where the invention is used, and behold it, as the writer did, performing smoothly and easily its regular routine work. Sitting near it, watching its movements, noting the deep yet slender groove it so swiftly cuts in the solid coal, and timing accurately its expert and quickly |