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The results obtained by the analysis of a fair sample of this product are as follow: Carbon, 90.94; hydrogen, 4.28; oxygen, 0 94; nitrogen, 1.25; sulphur, 1.18; and ash, 1.41.
From the Lancashire districts there were coal, cannel coal, and coke, the produce of the different seams worked by the Moss Hall Coal Company, at Ince, near Wigan. The coals from this part of England are of good quality, but are harder, and possess a more cubical fracture, than those from the South Wales coal fields; they likewise contain a larger proportion of ash, and give off considerable quantities of smoke when first lighted. The per-centage of hydrogen is, moreover, greater in these coals than in the Welsh varieties, and they are therefore used more frequently for the manufacture of gas. Caunel coal is a smooth, almost vitreous substance, with a conchoidal fracture, and brown, black color, and is chiefly employed for gas-making, for which its composition eminently adapts it. The cannel coal raised from the above mines is of good quality, and produces an extremely pure and highly illuminating gas. The composition of an average sample of cannel coal is as follows: Carbon, 80 21; hydrogen, 6.30; oxygen, sulphur, and nitrogen, 8.54; and ash, 4.95.
One ton of coal having the above composition will, on being carefully heated in proper retorts, yield 11,000 cubic feet of gas, capable of affording, during its combustion, an amount of light equal to that obtained from 1,150 best spermaceti candles. Coal of this description would be still more largely employed in our gas houses if the coke obtained from it were of good quality; but this is of such a crumbling nature, and possesses so little durability, as to be of no value except for the burning of lime, or similar purposes. The coals from the Derbyshire district are distinguished by a peculiar hackly structure, and a tendency to split into long prismatic fragments. They likewise contain a rather large per-centage of ash, and frequently iron pyrites and white shale. Among the specimens exhibited from this district are samples from the Butterly Iron Works near Alfreton, which very fairly represent the fossil fuel of the neighborhood, and of which the composition is, according to the official report, as follows: Butterly Company's Portland coal-carbon, 80.41; hydrogen, 4 65; nitrogen, 1.59; oxygen, 11.26; sulphur, 0.36; and ash, 1.23. This coal has a specific gravity of 1.301, and affords 60.90 percent. of friable coke.
The coals of Yorkshire have in general a more schistose appearance than those of the last-mentioned county, but they are nearly similar in point of composition and evaporative value. From the Staffordshire district some immense pieces were sent to the Exhibition. This variety affords, from the nature of its structure, great facilities for removal in large masses, as was seen from the block raised from the Denbigh Hall Colliery, near Tipton, and was found at the western entrance of the building.
In this department of the Exhibition were also found coals from the Scotch coal fields, and particularly from those in the neighborhood of Edinburg. Among these were samples from the Dalkeith Colliery, worked on the Midlothian coal seams. This coal is of the variety called "splint," and burns with a long flame and much smoke. It is also good for the purpose of gas-making, as may be inferred from the follow
ing analysis: Dalkeith coronation seam-carbon, 76.94; hydrogen, 5.20; nitrogen, trace of sulphur, 0.38; oxygen, 14.37; ash, 3.10.
Tin. In Cornwall most of the valleys in the tin districts produce sands containing the peroxide of that metal, which is extracted by subjecting them to a stream of water, where the greater density of the ore causes it to remain, while the lighter substances are carried away. The great proportion of tin raised, however, is procured from the mines; and as the process adopted with the best success in the oldest mining region in Europe cannot fail to be of use in the United States, it needs no apology for giving a detailed account of it here.
In order to ascertain the existence and direction of the mineral veins, what is called "shoding," or "costeaning," is adopted. When the general direction of the lodes of a neighborhood has been determined from other mines, a series of pits are sunk at right angles to the assumed run of these lodes. These pits are about three feet in width, six feet in length, and extend in depth through the alluvial deposit a few feet into the underlying well. In order to avoid the chance of missing any lode, the pits are sunk at regular distances, and are united by galleries from one to the other. Where the direction of the lodes is not known, two series of pits are arranged at right angles to each other.
When a lode has been discovered, the first operation is to drive what is called an adit level. This is a gallery cut a little above the level of the nearest valley, in such a way as to intersect the lode at a certain distance from the surface, and draw off the water from the higher portions of the vein. Should the appearance of the lode then prove favorable, a shaft is sunk to intersect the mineral deposit, to serve as the means of descending into the mine, and of removing the ore. Other shafts are then sunk, as occasion requires, and other levels are driven. Galleries are also excavated in the substance of the ore itself, for the purpose of extracting its contents. In the Cornish mines these galleries are at 10 fathoms distance.
The tools employed in tin-mining vary according to the nature of the ground. If the well be moderately soft, nothing more than an ordinary pick and shovel are used; but if it be hard, and is either stratified or contains numerous fissures, recourse is had to steel gads, or wedges, by driving which into the crevices of the rocks the miner is enabled to split off large portions. Gunpowder is also often used.
Copper. It was much to be regretted that the rich copper ore of the United States should not have been more fully represented at the Great Exhibition. There were, indeed, a few specimens, two of which, both for size and richness, were remarkable in comparison with all other samples of copper ore exhibited. But as an example of what our inexhaustible mines of copper are-as a fair exponent of what we are every year excavating from the earth, and what we are destined to excavate in years to come-these were, in fact, nothing.
The English collection of copper ores was very great. The owners and proprietors of the copper mines meant to convey a forcible idea of the source from whence the great mass of their commercial copper was obtained, and they succeeded. These specimens, however, consisted almost exclusively of what miners call yellow ore or copper pyrites. In this mineral, the copper is combined with iron and sulphur, which latter seldom reaches to less than 30 per cent. of the entire weight. In ex
tracting copper from copper prrites, it is customary to burn off the whole of this sulphur, and permit the resulting sulphurous and to pass away with the products of combustion from the furnace. This is the plan at present adopted, both in our own country and in all others where the metal is produced from this kind of raw material.
To say nothing of the intolerable nuisance thus created, it seems to involve also a great loss. English chemists are asking why this sulphurous acid should not be devoted to some use: and the question is certainly equally applicable to the United States. Estimates have been made, by which it was shown that at the mines of Swansea alone not less than 1,000 tons per week were thrown away. This amount, if converted into sulphuric acid, (an extremely marketable commodity,) would yield 2,700 tons of that substance: worth at least £2,500 sterling. Hence, the sulphur, equivalent to £1,500,000 worth of cil of vitriol, is every year converted into "thin air," and lost, at one English mine, through want of knowledge or skill to devise a means of securing or arresting sulphurous acid. It is true that sulphurous acid cannot be condensed. It is equally true, however, that it can be easily and cheaply converted into sulphuric acid; which last, as is known to all chemists, readily admits of condensation by steam or water alone. The mode of working sulphuret of iron is everywhere known, and it affords an exact analogy for guidance in the case of sulphuret of copper. When a small quantity of nitric oxide is added to sulphurous acid, in contact with water and air, sulphuric acid is the result; for this, in fact, constitutes the ordinary mode of making oil of vitriol. Moreover, as in the manufacture of oxalic acid this nitric oxide is itself a waste product, it surely would be worth while to try the effect of mixing these two valuable gases in a horizontal flue, containing a thin strature of water, or filled with pieces of pumice stone or coke, moistened with water. Suppose, for example, that the waste nitric oxide of an oxalic-acid maker were admitted into the sulphurous flue of copper works, is it not extremely probable that such an amount of condensation would ensue as to indemnify the trifling outlay of labor and expense consequent upon so simple a process? It may be urged, perhaps, that the sulphuric ac d so obtained must always contain arsenic, and, therefore, prove inadmissible for some purposes; but is not this already the case with sulphuric acid made from sulphuret of iron, which invariably contains arsenic?
Various plans have been devised for decomposing the sulphurous acid of copper works, by heating it in contact with hydrogen, or carbonic oxide gas, so as to deoxidize or reduce the sulphur it contains. But these have been unsuccessful, and are rather theoretical or retrogade movements made in the study than the practical experiments of business
Cobalt. The specimens of this metal from Great Britain were few. The richness, also, of those which were exhibited fell far below those which were to be found from the continent. Northern Germany exhibited many rich samples of that which has become to her free towns. and States a great source of commerce. Norway also exhibited a good number of samples, arranging them side by side with the results of their fusion, zaffre and speiss. The following remarks upon this subject, from Newton's London Journal and Repertory of Arts, are so well expressed, and bear so directly upon what may become a branch of industry in the United States, that we venture to insert them entire:
"Mingled with the beautiful samples of copper pyrites and argentiferous galena displayed in class No. 1 of the Great Exhibition, there are to be found several specimens of cobalt and nickel ores. These valuable articles lie buried beneath the huge bulk of their better-known compeers, and, unless sought for, will fail to arrest the attention even of a scientific observer; thus singularly illustrating, in the Crystal Palace, the obscure position they occupy in the manufacturing industry of the nation. The art of working the ores of cobalt and nickel seems unknown in Great Britain, if we may judge by the fact that, though found in sufficient abundance, they are nowhere, in this country, converted into zaffre and speiss, the two primary marketable products elsewhere obtained from these ores. Although, therefore, no nation in the world consumes, in its manufactures, more cobalt and nickel than Great Britain, yet, for these metals, it is entirely dependent upon Norway, northern Germany, and the Netherlands, from whence we import annually not less than 400 tons of zaffre and smalts, and nearly the same quantity of nickel and speiss, to the conjoint value of about £150,000 sterling. As these substances serve very different purposes in the arts, we propose to speak of them separately, merely premising that cobalt forms the basis of all the blue colors seen on earthenware, whilst nickel is an indispensable ingredient in the various metallic alloys known under the terms albata, German silver, &c. The specimens of ore previously alluded to as existing in the Great Exhibition have been derived from Cornwall, and contain, as is generally the case, both nickel and cobalt, thus far being precisely similar to the ores worked in Norway and northern Germany. The foreign ores are, however, much richer than the Cornish, since these latter seldom contain more than from two to seven per cent. of available metallic matter, whilst the former not unfrequently yield 12 or 15 per cent.; consequently, a process which answers quite well with the one may fail altogether, or prove profitless, with the other; and this is exactly the whole secret of our national failure in working cobalt ore.
"The Swedish method has been tried in several parts of Cornwall, and has not, in any one instance, given a satisfactory result; hence the Crystal Palace contains no specimen of British zaffre; and our potteries, glass works, and paper manufactories procure from abroad that which ignorance and apathy deny them at home. In the German ore the quantity of metallic ingredients is not only larger than in the Cornish, but also of a more fusible character; consequently, when simply subjected to heat in a reverberatory furnace, the earthy and metallic elements separate of themselves by the mere disparity of their specific weights, and the silicious gangue, with a portion of oxide of iron, rises to the top, leaving a metallic compound of arsenic, cobalt, nickel, copper, and perhaps iron, beneath. This latter, when carefully roasted in an oxidizing furnace, in contact with sand or ground flint, affords at once an impure silicate of cobalt and arseniuret of nickel-two marketable products. The Cornish ores, from their metallic poverty, will not undergo the first fusion neces sary to separate the silicious matrix of the mineral. And this trifling impediment seems actually to have benumbed the energy of that indomitable spirit of enterprise for which Britain is, in most things, justly celebrated. In the manufacture of iron, limestone is used to render the alumina and silica of the ore fusible; and, without this, no iron can be procured by the ordinary process. In roasting lead ore, lime cannot be
dispensed with. In copper-making not only lime, but also fluor spar, is frequently needed; and the commonest cobalt ores of Cornwall clearly require nothing but a proper flux to afford a compound of arsenic, cobali, and nickel, perfectly analogous to that procured from the German ore by mere fusion without a flux. The whole question, therefore, really resolves itself into the discovery of a cheap material, capable of easy vitrification with the granitic matrix of the Cornish ore, and which is nevertheless devoid of action upon the arseniurets of cobalt and nickel. The common fixed alkalies, though answering the first indication admirably, would not comply with the second condition; hence potash and soda-these great helpmates of industrial skill-are unfortunately ex cluded from the list of agents, as they act powerfully upon all the arseniurets, and would merely produce a worthless frit with the ore. Similar objections attach more or less to the alkaline earths, and therefore lime requires to be looked upon with suspicion. Borax would, and does yield a satisfactory result; but its high price is an insurmountable obstacle. Fluor spar is of no avail; and bottle glass requires too strong a temperature, and to be used in too great a quantity, for economical application to a mineral already surcharged with extraneous matters.
“These facts serve in some measure to explain, though we cannot al· low that they in any way justify, the present condition of the zaffre market, since these very difficulties are daily overcome in one of the largest metallurgical operations carried on amongst us. Many of the ores of copper, when first received by the manufacturer, are in a state quite parallel to that of the Cornish ores of cobalt, even in regard to poverty of metal: there is the same excess of granitic matrix, the same necessity for avoiding the use of any agent capable of attacking sulphuret of copper-a substance possessing very similar chemical affinities to those of the arseniurets of nickel and cobalt. What, then, is the flux employed by the copper manufacturer in such cases? We reply at once, it is the protoxide of iron, which is formed from these poor copper ores by the action of heat, and combines with the silica of the matrix, so as to pro. duce an extremely fusible silicate of iron, which permits the sulphuret of copper to fall down to the lower part of the reverberatory furnace, whilst the vitrified impurities of the ore are raked from its surface. Oxide of iron would most probably, therefore, enable a manufacturer accustomed to furnace operations to send into the market an arsenical compound of cobalt containing more than 50 per cent. of this metal, even if his interest failed to convince him of the great advantage resulting from its subsequent conversion into zaffre. Thus, then, the con. ditions of this seemingly difficult problem are answered, in a commercial sense; for oxide of iron is plentiful and cheap, its combination with silica is sufficiently fusible, and it has no action whatever upon metallic arseniurets. No doubt many other substances might be found equally applicable with the one we have mentioned; and, indeed, our object in thus dilating upon this and analogous topics, is rather to stimulate inquiry than lay down specific rules for practical guidance; consequently, our remarks must be regarded, at best, as but a shadowy outline, the manufacturing details of which require careful filling in to render the whole intelligible and useful.
"Before quitting the subject of cobalt, it may be as well to advert to a peculiar ore of that metal found near Keswick, in Cumberland. This