Various
Chambers's Edinburgh Journal, No. 458
This, no doubt, seems a great muster of evidence about so small a matter; but to judge of the rationality of its being entered upon, the reader must keep in mind the relation of the incident to others. If it only proved that the comic drinking-song The Whistle, and To Mary in Heaven, were written within three days of each other, it might be not altogether labour lost, for it would establish an exceedingly curious literary anecdote. But the bearing it has on the whole affair of Highland Mary—one of the most deeply interesting passages of Burns's life—is such as, in our opinion, to make every other justification superfluous.
VISIT TO THE COPPER-WORKS OF SWANSEA
Our first glimpse of the copper-works was obtained in the 'gloaming' of a lovely night in August last year, as we rattled over the Landore viaduct of the South Wales Railway. On each side of us, we could behold, given out by the chimneys, innumerable flashes of lurid flame, which rose like meteors into the atmosphere, and scattered around a brilliant light, that was seen in the distance to blend with the waters of Swansea Bay. The scene was very beautiful, and singularly picturesque: we could have wished our enjoyment of it prolonged; but soon the shrill whistle, the escape-valve, and the lamps of the station, admonished us that our journey had come to an end.
Our principal object in visiting Swansea, was to obtain some information concerning the important business of copper-smelting, for which this port has now become so celebrated. Few of our readers, who have not enjoyed our opportunities of seeing them, can form any accurate conception of the vast extent and great economical value and importance of the Swansea copper-works. Indeed, the copper trade is far from being popularly known; and the reason is obvious. Iron, which is very widely distributed in the British islands, is invariably smelted wherever it occurs. Copper, on the contrary, is only mined in one or two localities; and it is never manufactured on the spot. This process is performed almost exclusively at Swansea; and hence the copper trade of the country is confined to a few individual houses, and these are in a locality alike remote and unfrequented by the everyday tourist.
At the period when the first copper-work was established on the banks of the Tawy, about a century ago, Swansea was comparatively an insignificant village. It is therefore to this branch of industry the town and port are chiefly indebted for their remarkable rise and progress. The population in 1801 was only about 6000; while in 1851, if we include the copper-smelting district, it had already reached the number of 40,000. The original cause of Swansea being selected as the great seat of the copper trade, we may very briefly explain. It was early discovered that, from the non-existence of coal in the mining districts of Cornwall and Devonshire, copper, although raised in vast abundance, could not be profitably smelted there. In fact, it was not until a considerable time after copper-mining was properly pursued in Cornwall, that the minerals could be turned to a profitable account. It became apparent at length, however, both from the large quantity of coal necessary for the reduction of copper-ores, and the great expense of the transport, that instead of carrying coal to Cornwall to smelt the ores—the greater quantity to the less—an opposite course must be pursued, and the ores carried to the coal districts, and there smelted.
Now South Wales, poor in copper, is exceedingly rich in coal. Vast beds of the finest bituminous and anthracite coal exist in rich profusion in its inexhaustible coal-fields. From its geographical position and excellent harbour, Swansea was at once selected as the best port on the Welsh coast in which to establish the copper-works; and accordingly, the Swansea valley was soon planted with chimneys, furnaces, roasters, refiners, and, in short, all the necessary and costly enginery which belongs to the vast and intricate processes of smelting copper. With such propriety has the selection of a locality been made, that even now, out of the twenty copper-smelting works of which the country can boast, seventeen are situated on the navigable rivers of Swansea and its neighbourhood.
But this was not the only advantage the Cornish miners derived from this judicious step. The ships employed to transport the ore to South Wales came back laden with coal to feed their enormous engines; and thus a system of traffic, mutually advantageous, was originated, and has continued to exist without interruption down to the present time, and will continue to exist so long as copper is mined in Cornwall and smelted at Swansea.3
Within the last twenty years, the importation of foreign ores has become a remarkable feature in the trade and commerce of this place. Not only is Swansea the seat of the copper trade of this country, but it may with equal propriety be styled the copper mart of the world. Large and valuable cargoes of ore are continually arriving at the Swansea Docks from every country in the world where copper-mining is pursued. In 1814, there were only four vessels which traded with foreign ports; in 1849, this number had increased to 771; the greater proportion of them being directly engaged in the copper trade.
The Cornish ores are sold, as we have seen, in the locality in which they are produced; but all these foreign ores, from whatever quarter they may come, are disposed of to the smelters in Swansea by public ticketing. This ticketing is a curious and characteristic feature of the trade. The cargoes are usually consigned to a particular class of brokers, indigenous to Swansea, and known as 'copper-ore agents.' The ore is by them deposited in large yards, where it is crushed to a certain fineness, for the purpose of obtaining a proper admixture of the 'heap.' Notice is then given to the different smelting-houses, who procure samples of the lot, and assay it. Meetings are held once a fortnight at the Mackworth Arms Hotel; and on these days the agents for the ore and those for the smelter take their seats around a table. A chairman is appointed, who announces the different lots for sale. Having previously made up their minds what to offer—for there is nothing like a saleroom competition—the smelters hand up a folded slip to the chairman, who announces the highest offer and the purchaser's name. With such expedition does this proceed, that different cargoes of copper-ore, to the value perhaps of L.50,000, will often be quietly disposed of in a single hour!
It is very remarkable how closely each offer approximates to the intrinsic value of the ore. A lot of Chili or Australian ore, containing a large quantity of metal, may bring L.50 per ton, while at the same time a poor ore may be sold for a tenth part of the money. But however variable the offers may be in this respect, they never vary much in regard to a single lot. Out of the return of the twenty assayers of the different smelters, probably not a half per cent. of difference will be found in their estimates of the produce. The smelters having thus become possessed of the ore, it is transferred to their own yards, sometimes by means of lighters on the river, but more frequently by the canal which communicates with Swansea and the smelting-works.
Leaving the town, and pursuing our way northwards for two miles towards Neath, we reach the copper-works. The scene is widely different in open day from that which was presented at night. There is no beauty now, and little of the picturesque. The first impression, indeed, the mind is apt to receive, is that of a sense of painful weariness. Hundreds of chimneys—we speak literally—are vomiting forth that white, peculiar-looking, and unmistakable vapour called copper-smoke. Enormous masses of that ugly, black, silicious refuse, known in the smelting vocabulary as 'slag,' is piled above and around in such quantity as to change even the physical appearance of the country.
But this is not all. The noxious gases—which we see and feel around us—evolved in the reduction of copper, have not played so long on the surrounding atmosphere without doing their work. Everywhere within their influence, the perennial vegetation is meagre and stinted. The hills, particularly to the southeast of the copper-works, are barren in the extreme. Not one spark of green, not one solitary lichen, can withstand the ravages of the poison. Time was, we were told by an old inhabitant, when these hills produced the earliest and finest corn in the principality; but now they only resemble enormous piles of sandy gravel, unbroken but by the rugged angles on the face of the rock. In the year 1822, the inhabitants of Swansea took legal steps to abate the nuisance. A reward of L.1000 was likewise offered for the discovery of a successful means of neutralising the effect of the vapour. The Messrs Vivian of the Hafod Works spent the princely sum of L.14,000 in experiments, some of which were partially successful, and are still adopted; but after all, it must be confessed that the fumes of sulphurous acid, and of numerous other acids alike poisonous in their character, still taint the atmosphere of the Swansea valley, and still leave the indelible traces of their blasting properties.
The Hafod Works are the largest in South Wales. Situated on the north side of the river, they cover a superficial extent of about twenty acres. The number of furnaces, chimneys, and other brick erections contained in the works, was far beyond our computation; and we can speak feelingly of the devious ways and labyrinth of bypaths with which they are intersected, since, on more than one occasion, we became bewildered in their mazes.
Here was a group of workmen, half-naked, pouring out of a furnace the liquid copper at a white heat; there was another group with a red-hot copper-plate of colossal weight and dimensions, which they crushed like cheese between the huge rollers of the copper-mill: on one hand, there was an old furnace, that had done good duty in times past, in the process of being dismantled; on the other, was one about being rebuilt; and again there was still another, that had, from long service, become so impregnated with copper, that it was actually being built over by a larger one, to be melted in its turn!
We shall avail ourselves of the valuable services of Mr Morgan, the manager for Messrs Vivian, in our walks round the works, although it is not our intention to give a technical description of copper-smelting.4 Such a course would be alike uninteresting to the reader and unsatisfactory to ourselves. A consecutive description, however brief, of what we saw, would, in like manner, carry us far beyond our limits; and we therefore purposely confine ourselves to whatever is popularly interesting and instructive in the process.
First in order, then, we proceed to the ore-yard, which presents a very motley appearance. Under its capacious roof there were tons upon tons of every variety of ore—native and foreign, blue and red, green and yellow, and all intermediate colours—indiscriminately piled around. There was the beautiful green malachite from Australia, the gray sulphuret from Algiers, the phosphate from Chili, and the hydrous-carbonate from Spain. There was the glistening yellow sulphuret from Cuba, the silicate from Brazil, the bright-blue carbonate from the sunny regions of the south, and the dark-brown oxide from the colder regions of the north. There was regulus from New Zealand, and the good old pyrites from the Cornish mines; some compounds with arsenic, antimony, and numerous other substances; and last, though in one sense not least, there was a solitary specimen of ore from Ireland.
These ores were all in the form of a coarse powder. The regulus we have mentioned is simply the sulphuret deprived, by a preliminary operation, of its extraneous earthy matters; and this is frequently effected in the localities where it is produced, such as New Zealand and Chili, the expense of transport from these places being very considerable.
'And what is this?' we inquired, looking at a black earthy substance the workmen at that moment were discharging from a vessel.
'Ah!' said our friend, 'that is a commodity which, I suspect, you know something about. It is a waste product from certain foundries and chemical works—from Scotland in this case—and it contains a small per cent. of copper. We don't care much about it; we seldom have it; but it is sold at the ticketings regularly. For want of a better name, we term it slag; but it is not slag, properly so called, which you see all around you. A better denomination is that employed in designating it in the Journal—namely, rubbish.'5
'You make no kind of distinction in the ore-yard,' we continued. 'Is that unnecessary?'
'Well, practically it is. As these heaps lie, you can perceive that a vertical slice from top to bottom will give us a tolerably even admixture of the different ores. This is always desirable to a certain extent, since the ores being of different constitution, the one materially assists in the reduction of the other. Thus an ore containing a large proportion of fluor-spar may with great advantage be employed to flux another containing felspar or quartz, which substances are almost infusible alone. Indeed, the judicious admixture of ores constitutes the most important vocation of the smelter; and it is to this that the copper-houses of Swansea are indebted for one of their advantages over the proprietors of mines, who, possessing only one kind of ore—rich, probably, but intractable—can never bring it into the state of a metal with any satisfactory profit.'
'What is the value of these ores?'
'That varies much. This gray sulphuret contains about 70 per cent. of copper, and is worth L.35 per ton. This yellow sulphuret, from being mixed with a large quantity of iron and silicious earth, contains only about 12 or 14 per cent. Some malachites contain so much as 50 per cent., and others less pure, 30 to 40 per cent. of copper. But the greater mass of the ores we melt have a far less produce than this. That Cornish ore you see there, for example, contains only 4½ per cent. of metal. The average produce, however, of all the British and foreign ores smelted at Swansea may be given at about 12 per cent. Previous to the great increase of foreign importation, it was much lower.'
We now come to the process of smelting. The theory of reducing metallic ores, of whatever constitution, is to bring them to the state of oxides; and then, by the addition of charcoal, and with the aid of heat, to expel the oxygen in the form of carbonic acid; after which the pure metal is left. In practice, the reduction of copper-ores is slightly different. Here the object is to separate, first, the earthy matters and extraneous metals, by forming them into oxides by calcination: these are subsequently obtained as waste products in the form of slag; while the copper is left in combination with sulphur, which is then dispelled at one operation. According to Mr Vivian, copper undergoes eight, and sometimes nine, distinct operations in its progress from the ore to the ingot; and these consist of alternate calcinations and fusions, extending over a period of from 100 to 120 hours. As, however, some of these are simple repetitions, we may, for convenience' sake, illustrate the process under its three most important steps.
1. Calcination of the Ore.—Having arranged a proper mixture of ores in the yard, it is weighed out in boxes to the calcining-men. This is drawn up an inclined plane over the tops of the furnaces, and from thence emptied through hoppers, 3½ to 4½ tons at a time, into the large calcining furnace. Here it is roasted for a period ranging from twelve to twenty-four hours, after which it is drawn into the ash-pit, where it remains to cool. In this state, the ore is a black, amorphous substance, and is termed calcined ore. The object of this process is to oxidise the extraneous metals, and also to reduce the quantity of sulphur, by driving it off in the form of vapour. It is, therefore, in this and the analogous processes of roasting, that the sulphurous and arsenous vapours are so profusely given off.
We stood upon one occasion beside a furnace, when the charge was in the act of being withdrawn; but we took especial care never to do the like again. The sensation resembled what one might expect to feel on holding a lighted lucifer-match under each nostril. It is surprising how the workmen stand it. For the greater part of their lives, these poor Welshmen exist habitually in an atmosphere so charged with the above-mentioned abominable gases, that it is difficult to understand from whence their lungs receive the necessary supply of pure oxygen.6 Sulphurous acid, we may add, is the predominant smell in a copper-work; but arsenic acid, hydrofluoric acid, and even arseniuretted hydrogen, are not at all unfrequent.
2. Melting the Calcined Ore.—This is a totally different operation from the last: in place of roasting, it is one of fusion. The calcined ore is put into the furnace much in the same manner as before; a quantity of the slag from a subsequent process is added to assist in the fusion, and the heat is increased till the whole mass becomes liquid. The object is to separate the earthy matter, which, from being specifically lighter, rises to the surface of the liquid mass in the form of slag, and is drawn off. After two or three charges, the furnace becomes quite filled, and an aperture is then opened in it, through which the red-hot liquid flows into an adjoining pit filled with water. It is by this means granulated, and is now termed 'coarse metal,' or 'regulus;' and is, in fact, an admixture of the sulphurets of iron and copper, containing about 30 per cent. of the latter.
But it is to the earthy impurities here given off that we especially wish to direct attention. This slag, as it is termed, when drawn from the furnace, is run into oblong sand-moulds, from which, when cold, it is taken outside to the 'slag-bank,' as it is called—'slag-mountain,' we prefer saying; and an ugly mountain it is!—where it is broken into small pieces, examined to see whether it still contains metal, and if not, is left to accumulate. It consists essentially of silicon, oxygen, iron; or, to speak more correctly, it is a silicate of the protoxide of iron. It is, in fact, a true igneous rock. Portions of quartz and silica still remaining unfused, are often contained in the masses, which give to them, when broken, a true porphyritic appearance, while, from the great preponderance of the protoxide of iron, it is invariably black.
So hard, solid, and indurated do these slags, in process of time, become, that a very tall chimney, the most conspicuous object in the works, is built on the top of a slag-bank. And this beautiful commodity is not without its use in the arts. Part of it is occasionally cast into iron moulds, shaped like old Gothic arches, only uglier; and the casts are applied in great quantity as coping-stones to the walls and fences in the regions of the copper-works. Although not a very tasteful, it is yet a very useful, and, at the same time, a very characteristic application. We may add here, that the aggregate produce of the substance of the different Swansea works may be estimated at about 260,000 tons a year. Our readers may judge for themselves of the ultimate change this is calculated to bring about in the Carboniferous System, and of the learned controversies that are likely to arise among future geologists with respect to the character and constitution of these carefully disintegrated rocks!
To return to the smelting process. The last product—the regulus—is again calcined, with the view of bringing the iron to the state of an oxide. It is again melted, slagged, and run into pigs. In this last operation, the whole iron is driven out in the slag, and the remainder—'white metal,' as it is called—is almost a pure sulphuret of copper. The sulphur, having all along preserved its combination with the copper—a fine illustration of the theory of chemical attraction—must now at length be expelled. This is effected by the last process of roasting. When in a state of fusion in the furnace, the charge is exposed to a stream of air, in which case a double action ensues. Part of the oxygen enters into combination with the sulphur, producing sulphurous acid, which is expelled in the form of vapour, and part of it combines with the copper remaining in the furnace; this is again run out into the form of pigs, and in this state it is termed 'blistered copper.' To produce the finer kind of copper, another process has yet to be gone through; but for ordinary tough copper, it is at once transferred to what we may describe as the last stage, and that is—
3. Refining.—We quote Mr Vivian:—'The pigs from the roasters are filled into the furnace through a large door in the side: the heat is at first moderate, so as to complete the roasting or oxidising process; after the charge is run down, and there is a good heat on the furnace, the front door is taken down, and the slags skimmed off. An assay is then taken out by the refiner with a small ladle, and broken in the vice; and from the general appearance of the metal in and out of the furnace, the state of the fire, &c., he judges whether the toughening process may be proceeded with, and can form some opinion as to the quantity of poles and charcoal that will be required to render it malleable, or, as it is termed, to bring it to the proper pitch. The copper in this state is what is termed dry: it is brittle, of a deep-red colour, inclining to purple, an open grain, and crystalline structure. In the process of toughening, the surface of the metal in the furnace is first well covered with charcoal; a pole, commonly of birch, is then held into the liquid metal, which causes considerable ebullition, owing to the evolution of gaseous matter; and this operation of poling is continued, until, from the assays which the refiner from time to time takes, he perceives that the grain, which gradually becomes finer, is perfectly closed.' After some further manipulation of a similar kind, the refiner is at length satisfied of its malleability, and that the copper is now in its proper place, as he terms it. It is then poured out by means of iron ladles, coated with clay, into ingots or moulds of the different sizes required by the manufacturer.