Inventions in the Century

CHAPTER XIV.

METALLURGY

Ever since those perished races of men who left no other record but that engraven in rude emblems on the rocks, or no other signs of their existence but in the broken tools found buried deep among the solid leaves of the crusted earth, ever since Tubal Cain became "an instructor of every artificer in brass and iron," the art of smelting has been known. The stone age flourished with implements furnished ready-made by nature, or needing little shaping for their use, but the ages of metal which followed required the aid of fire directed by the hand of man to provide the tool of iron or bronze.

The Greeks claimed that the discovery of iron was theirs, and was made at the burning of a forest on the mountains of Ida in Crete, about 1500 B. C., when the ore contained in the rocks or soil on which the forest stood was melted, cleansed of its impurities, and then collected and hammered. Archeologists have deprived the Greeks of this gift, and carried back its origin to remoter ages and localities.

Man first discovered by observation or accident that certain stones were melted or softened by fire, and that the product could be hammered and shaped. They learned by experience that the melting could be done more effectually when the fuel and the ore were mixed and enclosed by a wall of stone; that the fire and heat could be alone started and maintained by blowing air into the fuel – and they constructed a rude bellows for this purpose. Finding that the melted metal sank through the mass of consumed fuel, they constructed a stone hearth on which to receive it. Thus were the first crude furnace and hearth invented.

As to gold, silver and lead, they doubtless were found first in their native state and mixed with other ores and were hammered into the desired shapes with the hardest stone implements.

That copper and tin combined would make bronze was a more complex proceeding and probably followed instead of preceding, as has sometimes been alleged, the making of iron tools. That bronze relics were found apparently of anterior manufacture to any made of iron, was doubtless due to the destruction of the iron by that great consumer – oxygen.

What was very anciently called "brass" was no doubt gold-coloured copper; for what is modernly known as brass was not made until after the discovery of zinc in the 16th century and its combination with copper.

Among the "lost arts" re-discovered in later ages are those which supplied the earliest cities with ornamented vessels of gold and copper, swords of steel that bent and sprung like whalebones, castings that had known no tool to shape their contour and embellishments, and monuments and tablets of steel and brass which excite the wonder and admiration of the best "artificers in brass and iron" of the present day.

To understand and appreciate the advancements that have been made in metallurgy in the nineteenth century, it is necessary to know, in outline at least, what before had been developed.

The earliest form of a smelting furnace of historic days, such as used by the ancient Egyptians, Hebrews, and probably by the Hindoos and other ancient peoples, and still used in Asia, is thus described by Dr Ure:

"The furnace or bloomary in which the ore is smelted is from 4 to 5 feet high; it is somewhat pear-shaped, being about 5 feet wide at bottom and 1 at top. It is built entirely of clay. There is an opening in front about a foot or more in height which is filled with clay at the commencement, and broken down at the end of each smelting operation. The bellows are usually made of two goatskins with bamboo nozzles, which are inserted into tubes of clay that pass into the furnace. The furnace is filled with charcoal, and a lighted coal being introduced before the nozzle, the mass in the interior is soon kindled. As soon as this is accomplished, a small portion of the ore previously moistened with water to prevent it from running through the charcoal, but without any flux whatever, is laid on top of the coals, and covered with charcoal to fill up the furnace. In this manner ore and fuel are supplied and the bellows urged for three or four hours. When the process is stopped and the temporary wall in front broken down the bloom is removed with a pair of tongs from the bottom of the furnace."

This smelting was then followed by hammering to further separate the slag, and probably after a reheating to increase the malleability.

It will be noticed that in this earliest process pure carbon was used as a fuel, and a blast of air to keep the fire at a great heat was employed. To what extent this carbon and air blast, and the mixing and remixing with other ingredients, and reheating and rehammering, may have been employed in various instances to modify the conditions and render the metal malleable and more or less like modern steel, is not known, but that an excellent quality of iron resembling modern steel was often produced by this simple mode of manufacture by different peoples, is undoubtedly the fact. Steel after all is iron with a little more carbon in it than in the usual iron in the smelting furnace, to render it harder, and a little less carbon than in cast or moulded iron to render it malleable, and in both conditions was produced from time immemorial, either by accident or design.

It was with such a furnace probably that India produced her keen-edged weapons that would cut a web of gossamer, and Damascus its flashing blades – the synonym of elastic strength.

Africa, when its most barbarous tribes were first discovered, was making various useful articles of iron. Its earliest modes of manufacture were doubtless still followed when Dr Livingstone explored the interior, as they now also are. He thus describes their furnaces and iron: "At every third or fourth village (in the regions near Lake Nyassa) we saw a kiln-looking structure, about 6 feet high and 2½ feet in diameter. It is a clay fire-hardened furnace for smelting iron. No flux is used, whether with specular iron, the yellow hematite, or magnetic ore, and yet capital metal is produced. Native manufactured iron is so good that the natives declare English iron "rotten" in comparison, and specimens of African hoes were pronounced at Birmingham nearly equal to the best Swedish iron." The natives of India, the Hottentots, the early Britons, the Chinese, the savages of North and South America, as discovery or research brought their labours to light, or uncovered the monuments of their earliest life, were shown to be acquainted with similar simple forms of smelting furnaces.

Early Spain produced a furnace which was adopted by the whole of Europe as fast as it became known. It was the Catalan furnace, so named from the province of Catalonia, where it probably first originated, and it is still so known and extensively used. "It consists of a four-sided cavity or hearth, which is always placed within a building and separated from the main wall thereof by a thinner interior wall, which in part constitutes one side of the furnace. The blast pipe comes through the wall, and enters the fire through a flue which slants downward. The bottom is formed of a refractory stone, which is renewable. The furnace has no chimneys. The blast is produced by means of a fall of water usually from 22 to 27 feet high, through a rectangular tube, into a rectangular cistern below, to whose upper part the blast pipe is connected, the water escaping through a pipe below. This apparatus is exterior to the building, and is said to afford a continuous blast of great regularity; the air, when it passes into the furnace, is, however, saturated with moisture." —Knight.

No doubt in such a heat was formed the metal from which was shaped the armour of Don Quixote and his prototypes.

Bell in his history of Metallurgy tells us that the manufacture of malleable iron must have fallen into decadence in England, especially before the reign of Elizabeth and Charles I., as no furnaces equal even to the Catalan had for a long time been in use; and the architectural iron column found in ancient Delhi, 16 inches in diameter, about 48 feet long and calculated to weigh about 17 tons, could not have been formed by any means known in England in the sixteenth century. This decadence was in part due to the severe laws enacted against the destruction of forests, and most of the iron was then brought to England from Germany and other countries.

From time immemorial the manufacture of iron and steel has been followed in Germany, and that country yet retains pre-eminence in this art both as to mechanical and chemical processes. It was in the eighteenth century that the celebrated Freiberg Mining Academy was founded, the oldest of all existing mining schools; and based on developing mining and metallurgy on scientific lines, it has stood always on the battle line in the fight of progress.

The early smelting furnaces of Germany resembled the Catalan, and were called the "Stückofen," and in Sweden were known as the "Osmund." In these very pure iron was made.

The art of making cast iron, which differs from the ordinary smelted iron in the fact that it is melted and then run into moulds, although known among the ancients more than forty centuries ago, as shown by the castings of bronze and brass described by their writers and recovered from their ruins, appears to have been forgotten long before the darkness of the middle ages gathered. There is no record of its practice from the time the elder Pliny described its former use (40-79 A. D.), to the sixteenth century. It is stated that then the lost art was re-invented by Ralph Page and Peter Baude of England in 1543 – who in that year made cast-iron in Sussex.

The "Stückofen" furnace above referred to was succeeded in Germany by higher ones called the "Flossofen," and these were followed by still higher and larger ones called "Blauofen," so that by the middle of the eighteenth century the furnaces were very capacious, the blast was good, and it had been learned how to supply the furnaces with ore, coal and lime-stone broken into small fragments. The lime was added as a flux, and acted to unite with itself the sand, clay and other impurities to form a slag or scoria. The melted purified iron falling to the bottom was drawn off through a hole tapped in the furnace, and the molten metal ran into channels in a bed of sand called the "Sow and pigs." Hence the name, "pig iron."

The smelting of ore by charcoal in those places where carried on extensively required the use of a vast amount of wood, and denuded the surrounding lands of forests. So great was this loss felt that it gave rise to the prohibitory laws and the decadence in England of the manufacture of iron, already alluded to. This turned the attention of iron smelters to coal as a substitute. Patents were granted in England for its use to several unsuccessful inventors. Finally in 1619 Dud Dudley, a graduate of Oxford University, and to whom succeeded his father's iron furnaces in Worcestershire, obtained a patent and succeeded in producing several tons of iron per week by the use of the pitcoal in a small blast furnace.

This success inflamed the wood owners and the charcoal burners and they destroyed Dudley's works. He met with other disasters common to worthy inventors and discontinued his efforts to improve the art.

It is said that in 1664 Sir John Winter of England made coke by burning sea coal in closed pots. But this was not followed up, and the use of charcoal and the destruction of the forests went on until 1735, when Abraham Darby of the Coalbrookdale Iron Works at Shropshire, England, commenced to treat the soft pit coal in the same way as wood is treated in producing charcoal. He proposed to burn the coal in a smouldering fire, to expel the sulphur and other impurities existing in the form of phosphorus, hydrogen and oxygen, etc. while saving the carbon. The attempt was successful, and thus coke was made. It was found cheaper and superior to either coal or charcoal, and produced a quicker fire and a greater heat. This was a wonderful discovery, and was preserved as a trade secret for a long time. It was referred to as a curiosity in the Philosophical Transactions in 1747. In fact it was not introduced in America until a century later, when in 1841 the soft coal abounding around Pittsburgh in Pennsylvania and in the neighbouring regions of Ohio was thus treated. Even its use then was experimental, and did not become a practical art in the United States until about 1860.

With the invention of coke came also the revival of cast iron.

The process of making cast steel was reinvented in England by Benjamin Huntsman of Attercliff, near Sheffield, about 1740. Between that time and 1770 he practised melting small pieces of "blistered" steel (iron bars which had been carbonised by smelting in charcoal) in closed clay crucibles.

In 1784 Henry Cort of England introduced the puddling process and grooved rolls. Puddling had been invented, but not successfully used before. The term "puddling" originated in the covering of the hearth of stones at the bottom of the furnace with clay, which was made plastic by mixing the clay in a puddle of water; and on which hearth the ore when melted is received. When in this melted condition Cort and others found that the metal was greatly improved by stirring it with a long iron bar called a "rabble," and which was introduced through an opening in the furnace. This stirring admitted air to the mass and the oxygen consumed and expelled the carbon, silicon, and other impurities. The process was subsequently aided by the introduction of pig iron broken into pieces and mixed with hammer-slag, cinder, and ore. The mass is stirred from side to side of the furnace until it comes to a boiling point, when the stirring is increased in quickness and violence until a pasty round mass is collected by the puddler. As showing the value of Cort's discovery and the hard experience inventors sometimes have, Fairbairn states that Cort "expended a fortune of upward of £20,000 in perfecting his invention for puddling iron and rolling it into bars and plates; that he was robbed of the fruits of his discoveries by the villainy of officials in a high department of the government; and that he was ultimately left to starve by the apathy and selfishness of an ungrateful country. His inventions conferred an amount of wealth on the country equivalent to £600,000,000, and have given employment to 600,000 of the working population of our land for the last three or four generations." This process of puddling lasted for about an hour and a half and entailed extremely severe labour on the workman.

The invention of mechanical puddlers, hereinafter referred to, consisting chiefly of rotating furnaces, were among the beneficent developments of the nineteenth century.

Prior to Cort's time the plastic lump or ball of metal taken from the furnace was generally beaten by hammers, but Cort's grooved rollers pressed out the mass into sheets.

The improvements of the steam engine by Watt greatly extended the manufacture of iron toward the close of the 18th century, as powerful air blasts were obtained by the use of such engines in place of the blowers worked by man, the horse, or the ox.

So far as the art of refining the precious metals is concerned, as well as copper, tin and iron, it had not, previous to this century, proceeded much beyond the methods described in the most ancient writings; and these included the refining in furnaces, pots, and covered crucibles, and alloying, or the mixture and fusion with other metals. Furnaces to hold the crucibles, and made of iron cylinders lined with fire brick, whereby the crucibles were subjected to greater heat, were also known.

The amalgamating process was also known to the ancients, and Vitruvius (B. C. 27) and Pliny (A. D. 79), describe how mercury was used for separating gold from its impurities. Its use at gold and silver mines was renewed extensively in the sixteenth century.

Thus we find that the eighteenth century closed with the knowledge of the smelting furnaces of various kinds, of coke as a fuel in place of charcoal, of furious air blasts driven by steam and other power, of cast iron and cast steel, and of refining, amalgamating, and compounding processes.

Looking back, now, from the threshold of the nineteenth century over the path we have thus traced, it will be seen that what had been accomplished in metallurgy was the result of the use of ready means tested by prolonged trials, of experiments more or less lucky in fields in which men were groping, of inventions without the knowledge of the real properties of the materials with which inventors were working or of the unvarying laws which govern their operations. They had accomplished much, but it was the work mainly of empirics. The art preceding the nineteenth century compared with what followed is the difference between experience simply, and experience when combined with hard thinking, which is thus stated by Herschel: "Art is the application of knowledge to a practical end. If the knowledge be merely accumulated experience the art is empirical; but if it is experience reasoned upon and brought under general principles it assumes a higher character and becomes a scientific art."

With the developments, discoveries and inventions in the lines of steam, chemistry and electricity, as elsewhere told, the impetus they gave to the exercise of brain force in every field of nature at the outset of the century, and with their practical aid, the art of metallurgy soon began to expand to greater usefulness, and finally to its present wonderful domain.

The subject of metallurgy in this century soon became scientifically treated and its operations classified.

Thus the physical character and metallic constituents of ores received the first consideration; then the proper treatment to which the ores were to be subjected for the purpose of extracting the metal – which are either mechanical or chemical. The mechanical processes designed to separate the ore from its enclosing rock or other superfluous earthy matter called gangue became known as ore dressing and ore concentrating. These included mills with rollers, and stamps operated by gravity, or steam, for breaking up the ore rocks; abrasion apparatus for comminuting the ore by rubbing the pieces of ore under pressure; and smelting, or an equivalent process, for melting the ore and driving off the impurities by heat, etc. The chemical processes are those by which the metal, whatever it may be, is either dissolved or separated from other constituents by either the application to the ore of certain metallic solutions of certain acids, or by the fusion of different ores or metals in substantially the old styles of furnaces; or its precipitation by amalgamating, or by electrolysis – the art of decomposing metals by electricity.

In the early decades of the century, by the help of chemistry and physics, the nature of heat, carbon, and oxygen, and the great affinity iron has for oxygen, became better known; and particularly how in the making of iron its behaviour is influenced by the presence of carbon and other foreign constituents; also how necessary to its perfect separation was the proper elimination of the oxygen and carbon. The use of manganese and other highly oxidisable metals for this purpose was discovered.