THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN COLLIERY TROLLEY.THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN COLLIERY TROLLEY.
THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN COLLIERY TROLLEY.
THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN COLLIERY TROLLEY.
THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN COLLIERY TROLLEY.This locomotive was constructed in 1813 at Wylam Colliery, England, by William Hedley. It was entirely successful, and was in operation for almost half a century, up to the time of its removal in 1862 to the South Kensington Museum. The vertical cylinders and arrangement of walking beams for transmitting power are particularly interesting. The power was transmitted through cogged wheels to the rear axle, as is done with modern automobiles.
This locomotive was constructed in 1813 at Wylam Colliery, England, by William Hedley. It was entirely successful, and was in operation for almost half a century, up to the time of its removal in 1862 to the South Kensington Museum. The vertical cylinders and arrangement of walking beams for transmitting power are particularly interesting. The power was transmitted through cogged wheels to the rear axle, as is done with modern automobiles.
This locomotive was constructed in 1813 at Wylam Colliery, England, by William Hedley. It was entirely successful, and was in operation for almost half a century, up to the time of its removal in 1862 to the South Kensington Museum. The vertical cylinders and arrangement of walking beams for transmitting power are particularly interesting. The power was transmitted through cogged wheels to the rear axle, as is done with modern automobiles.
A particular advantage has been gained by the use of electric locomotives over older methods in the process of "gathering" the cars. In many coal mines, even when the main hauling is done by electricity, the gathering or collecting of cars from the working faces of the rooms was formerly done either by mule-power or by hand. In some low-veined mines, hand power alone was used, on account of the low roof.
In such places, low, compressed-air locomotives were sometimes used; but these were very expensive. These have now been very generally replaced by "turtle-back" electric locomotives, operated at a distance from the main trolley wire by means of long, flexible cables, so geared that they can be paid out or coiled as desired.
On the main line these locomotives take the current from the trolley wire by means of the trolley pole, but when the place for gathering is reached, the connection is made by means of the flexible cable, and the trolley pole fastened down so as not to be in the way. This allows the locomotive to push the little cars into the rooms far removed from the main line, with passagestoo low and narrow to allow the use of the trolley pole. By the time the last cars have been delivered the first cars of the train have been filled, and the process of gathering may be begun at once, and the loaded train made up for the return trip. With such a locomotive two men can distribute and gather up from one hundred to one hundred and twenty cars in an ordinary eight-hour working-day, hauling from three hundred to three hundred and fifty tons of coal.
In certain regions, a system of third-rail current-supply is used, this rail being also a tooth rail with which a cog on the locomotive works frictionally. For climbing steep grades this system of cogged rails has many advantages over other systems.
Another type of electric locomotive used in some mines is a self-propelling or automobile one equipped with storage batteries. Such locomotives do away with the inconvenience and dangers of contact rails or trolley wires, but are heavy and expensive. A compromise locomotive, particularly useful for gathering, is one equipped with both trolley pole and storage batteries. This locomotive is so made that the storage batteries are charged while it is running with the trolley connection, so that no time is lost in the charging process. Such locomotives have been found very satisfactory for many purposes, and but for the imperfections common to all storage batteries would be ideal in many ways. They can be worked over any improvised track, regardless of distance, which is an advantage over the flexible-cable system where distances are limited by the length of cable; and thefirst cost of the battery is no more than the outlay on trolley wires and supports. It is also claimed that the cost of maintenance is relatively low, but it is doubtful if it equals the trolley or third-rail systems in this respect.
Closely allied to the systems of traction by electric locomotives, is the modern electric telpherage system. Until quite recently the haulage of ores and other raw materials used in mining, when done aerially, has been by means of travelling rope or cable. When distances to be travelled in this manner are short, such as across streams or valleys, where no supports are used, the term "cableway" is generally applied; but where the distance is so long that supports are necessary, the term "tramway cable" is used. It is to these longer systems that electric telpherage is particularly applicable.
The advantage of such an electric system over the older method is the same as the advantages of the trolley road over the cable, all ropes and cables being stationary, the electric motor, or "telpher," travelling along on one cable and taking its current by means of a trolley pole from a wire above. For heavier work metal rails supported between posts are employed in place of a flexible cable, and over such systems loads of several tons can be hauled.
Such an electric telpher system is used in one of the Cuban limestone quarries, the telpher and cars travelling a long distance upon cables, except at some of the curves, where solid rails are substituted, hauling a load of a thousand pounds at a speed of from twelve to fifteen miles an hour. The current comes from a distant source, and the telpher is so arranged that ittravels automatically when the current is turned on, stopping when the current is cut off. This is quite a common arrangement for smaller telphers, but in the larger ones a man travels with the telpher and load, controlling the train just as in the case of the ordinary trolley system.
The various processes of hoisting in mines by electricity is closely akin to that of traction, since, after all, "an elevator is virtually a railway with a 100-per-cent grade." As such work is done spasmodically, long periods of rest intervening between actual periods of work, a great deal of energy is wasted by steam hoisting engines, where a certain pressure of steam in the boiler must be maintained at all times. For this reason electrical energy for hoisting has come rapidly into popularity in recent years. "The throttling of steam to control speed," said Mr. F. O. Blackwell in addressing the American Institute of Mining Engineers, "the necessity for reversing the engine, the variation in steam pressure, the absence of condensing apparatus, the cooling and large clearance of cylinders, and the condensation and leakage of steam pipes when doing no work, are all against the steam hoisting engine. One of the largest hoisting engines in the world was recently tested and found to take sixty pounds of steam per indicated horse-power per hour. The electric motor, on the other hand, is ideal for intermittent work. It wastes absolutely no energy when at rest, there being no leakage or condensation. Its efficiency is high, from one-quarter load to twice full load."
There seems to be practically no difference as far asthe element of danger is concerned between steam and electric hoists. The difference is largely one of economy. The importance of this is shown by the recent comparisons in a gold mine which has replaced its steam apparatus by electricity. In this mine the hoist moves through the shaft at a rate of over twelve hundred feet per minute, elevating five hundred tons of ore daily on double-decked cages. It is estimated that this system shows an efficiency of 75 per cent, taking into account losses of all kinds, with a resulting reduction of cost of from seven to twenty dollars per horse-power per month.
Results comparing very favorably with these have been obtained also in some of the mines in Germany and Bohemia, where electricity has been introduced extensively in mining. In one of these mines the daily hoisting capacity is twenty-seven hundred tons from a depth of over sixteen hundred feet, at a speed of over fifty-two feet per second. In the Comstock mine, at Virginia City, Nev., electric hoists are used which obtain their power from a plant situated on the Truchee River thirty-two miles away.
In pumping, which is always one of the important items in mining, the use of electric power has been found quite as advantageous as in the other fields of its application. No special features are embodied in most of the types of mining pumps over the rotary and reciprocating types used for ordinary purposes,except perhaps a type of pump known as the sinking pump. This is a movable pump that can be easily lowered from one place to another, and has proved to be a great time-saver over steam or air pumps used for similar purposes.
For some time the question of the durability of electric pumps was in dispute, but developments in quite recent years seem to prove that, in some instances at least, such pumps are practically indestructible.
"The question of what would happen to an electric motor in a mine if pumps and motors get flooded has often come up. From tests made recently at the University ofLiège, Belgium, it appears that a suitably designed polyphase alternating-current motor of a type largely used on the continent of Europe was completely submerged in water. It was run for a quarter of an hour; it was then stopped and allowed to remain submerged, under official seal, for twenty-four hours, at the end of which time it was again run for a few minutes. It was next removed from the water, again put under seal, and left to dry for twenty-four hours. The insulation was then tested, and the motor was found to be in perfect order. It would be hard to imagine a test more severe than this.
"As bearing upon this question it is interesting to note that among the pumps in use around Johannesburg, South Africa, at the beginning of the Anglo-Boer War, there were twelve of a well-known American make, each of which was operated by a 50-horse-power induction motor of American construction with three 15-kilowatt transformers. When the mines wereshut down, upon the breaking out of the war, the water rose so rapidly that it was impossible to remove the pumps, motors, transformers, etc., and consequently they remained under 500 to 1,000 feet of water. Two and a half years later, when peace was declared in South Africa, the water in the shaft was pumped out and the electrical apparatus was removed to the surface. Three of the motors were stripped and completely rewound, but to the general surprise of the experts the condition of the insulation indicated that the rewinding might not be absolutely necessary. Accordingly the other nine motors were thoroughly dried in an oven and then soaked in oil. After this treatment they were rigidly tested, proved to be all right, and were at once restored to regular service in the mine. The transformers were treated in the same manner as the motors, with equally gratifying results.
"An interesting illustration of the flexibility and adaptability of electric motors for pumping purposes is furnished by the Gneisenau mine, near Dortmund, Germany, where a very large electric mining plant was installed in 1903. In this instance the pump is located more than 1,200 feet below the surface, and the difficulties of installing the apparatus were so great, on account of the small cross section of the shaft, that it was necessary to build up the motor in the pumping chamber, the material being transported through the wet shaft and the winding of the coils being performedin situ.
"An interesting use of the electric pump associated with the telephone in connection with mining is notedby Mr. W. B. Clarke. In one coal mine, where an electric pump is located in a worked-out portion of the mine, the circuits are so arranged that the pump is started from the power house, some distance away. Near the pump is placed a telephone transmitter connected to a receiver in the power house. To start the motors, or to ascertain whether the pumps are working properly, the engineer merely listens at the telephone receiver, without leaving his post."
In coal mining the effect of the use of electrical machinery has been revolutionary in recent years, particularly in the development of electric coal cutters. The old method of picking out coal by hand, where the miner labored with the heavy pick, working in all manner of cramped and dangerous positions, was supplanted a few years ago by the "puncher" machine, worked by steam or compressed air. With these machines the coal was picked out just as in the case of the hand method, except that the energy was derived from some power other than muscular. So that while these machines worked more rapidly than the hand picks, they utilized the same general principle in applying their energy.
Within recent years, however, various coal-cutting machines have been devised, with which the coal was actually cut, or sawed out, these machines being peculiarly well adapted to using the electric current. The most practical and popular form of machine isone in which the sawing is done by an endless chain, the links of which are provided with a cutting blade. These have been very generally replacing the compressed-air or pick type of machine, and their popularity accounts largely for the enormous increase in the use of coal-mining machinery during the past decade. Thus in 1898 there were 2,622 coal-mining machines in use in the United States. Four years later this number had more than doubled, the increase being due largely to the adoption of chain machines.
Like electric locomotives, and for similar reasons, the coal-cutting machines are low, broad, flat machines, from eighteen to twenty-eight inches high. They rest upon a flat shoeboard that can be moved easily along the face of the coal. An ordinary machine weighs in the neighborhood of a ton, and requires two men to operate. The apparatus is described briefly as follows:
"On an outside frame, consisting of two steel channel bars and two angle irons riveted to steel cross ties, rests a sliding frame consisting of a heavy channel or centre rail, to which is bolted the cutter head. The cutter head is made entirely of two milled steel plates, which bolt together, forming the front guide for the cutter chain. This chain, which is made of solid cast steel links connected by drop forge straps, is carried around idlers or sprockets placed at each end of the cutter head and along the chain guides at the side to the rear of the machine, where it engages with and receives its power from a third sprocket, under the motor. The electric motor, which is of ironcladmultipolar type, rests upon a steel carriage, which forms the bearing for the main shaft.... A reversing switch is provided, so that the truck can travel in either direction, and when the machine has reached its stopping point, either forward or backward, it is checked by an automatic cut-off. The return travel is made in about one-fourth of the time required to make the cut."
In veins of coal of a thickness from twenty-eight to thirty inches, such a machine will cut about one hundred tons of coal in a day. The cost of production with such machines has been estimated at about sixty-three cents a ton, as against ninety cents as the cost of pick mining in rooms,—a saving of about twenty-seven cents a ton. Since it is estimated that for a cost of $10,000 an electrical equipment can be installed capable of working four such machines besides affording power for lighting, pumping, ventilation of the mine, etc., thus saving something like $100 a day for the operator, the great popularity of these machines is readily understood.
After such a machine has been placed in position, a cut some four feet wide, four or five inches high, and six feet deep can be made in five minutes, with the expenditure of very little energy on the part of the workmen. One of the largest cuttings ever recorded by one of these machines is 1,700 square feet in nine and one-half hours, although this may have been exceeded and not recorded.
Among the several advantages claimed for the chain machine over the older pick machines is the small amount of slack coal produced, and the absence ofthe racking vibrations that exhaust the workmen, and, like the air drills, sometimes cause serious diseases. On the other hand the advocates of the pick machines point out that they can be used in mines too narrow for the introduction of chain machines. They show also that there is a constant element of danger from motor-driven machines in mines where the quantity of gas present makes it necessary to use safety lamps, on account of the sparking of the machines which may produce explosions. Both these claims are valid, but apply only to special cases, or to certain mines, and do not affect the general popularity of the chain machines.
There are several different types of chain cutting machines, such as "long-wall machines," and "shearing machines," but these need not be considered in detail here. The general principle upon which they work is the same as the ordinary chain machine, the difference being in the method of applying it for use in special situations.
For many obvious reasons the ideal light for mining purposes is one in which the danger from the open flame is avoided, particularly in well-ventilated mines, or mines under careful supervision, where the danger from inflammable gases is slight. The incandescent electric light, therefore, has become practically indispensable in modern mining operations. For certain purposes and in certain locations where an intenselight is desirable and where there is no danger from combustible gases, arc lights are used to a limited extent. But there is constant danger from the open flame in using such lights, and also from the connecting wires leading to them. Furthermore, such intense light is not usually necessary in the narrow passages of the mine.
To be sure, there is a certain element of danger even with incandescent lights on account of the possibility of breakage of the globes, and of short-circuiting where improper wiring has been done. To overcome as much as possible the dangers from these sources, special precautions are taken in wiring mines, and special bulbs are used. In general the incandescent lamps as used in mining are made of stout round bulbs of thick glass which are not likely to crack from the effects of water dripping upon them while heated. As a further protection it is customary to enclose the bulbs in wire cages. It is also customary to use low-current lamps with a rather high voltage, although this must be limited, as excessive voltage may in itself become a source of danger.
Theiron industry has of late years become more and more merged into the steel industry, as steel has been gradually replacing the parent metal in nearly every field of its former usefulness. Steel is so much superior to iron for almost every purpose and the process of making it has been so simplified by Bessemer's discovery that it may justly be said that civilization has emerged from the Iron Age, and entered the Age of Steel. While iron is mined more extensively now than at any time in the history of the world, the ultimate object of most of this mining is to produce material for manufacturing steel. We still speak of boiler iron, railroad iron, iron ships, etc., but these names are reminiscent, for in the construction of modern boilers and modern ships, steel is used exclusively. In the past decade it is probable that no railroad rails even for the smallest and cheapest of tracks have been made of anything but steel.
The last half of the nineteenth century has been one of triumph of steel manufacture and production in America, and at the present time the United States stands head and shoulders above any other nation in this industry. In the middle of the century bothGermany and England were greater producers than America; but by the close of the century the annual output in the United States was above fifteen million tons as against England's ten and Germany's seven; and since 1900 this lead has been greatly increased. The steel industry has become so great, in fact, that it is "a sort of barometer of trade and national progress."
The great advances in the quantity of steel produced have been made possible by corresponding advances in methods of winning the iron ore from the earth. Mining machinery has been revolutionized at least twice during the last half century, first by improved machines driven by steam, and again by electricity and compressed air. Ore is still mined to a limited extent by men with picks and shovels, but these implements now play so insignificant a part in the process that they cannot be considered as important factors. Steam shovels, automatic loaders and unloaders, dynamite and blasting powder, have taken the place of brawn and muscle, which is now mostly expended in directing and guiding mining machinery rather than in actually handling the ore.
At the present time the greatest iron-ore fields lie in the Lake Superior region, and it is in this region that the greatest progress in mining methods has been made in recent years. There are, of course, extensive mines in other sections of the United States, but at least three-quarters of all the iron produced in Americacomes from the Lake Superior mines, and the systems of mining pursued there may be considered as representative of the most advanced modern methods.
Where the iron ore of these mines is found near the surface of the earth, the great system of "open-pit" mining is practised; but as only a relatively small portion of the ore is so situated, modifications of older mining methods are still employed. Of these the three most important are known as "overhead scooping," "caving," and "milling."
In the overhead method a shaft is sunk into the earth to a depth of several hundred feet, according to the depth of the ore, this shaft being lined with timbers for support. From this shaft horizontal tunnels are made in all directions in the ore deposits, and through these tunnels the ore is conveyed to the shaft and thence to the surface. As the ore is removed and the earth thus honeycombed in all directions, supports of various kinds must be made to prevent caving. For this purpose columns of the ore itself may be left, or supports of masonry or wood or steel may be introduced. Under certain circumstances, however, these supports are not employed, the earth being allowed gradually to cave in at the surface as the ore is removed, this being the method of mining known as "caving."
Where the ore deposit occurs in a favorable hillside the "milling" system is frequently employed. In working this system a large horizontal tunnel, twenty or more feet in diameter, is dug into the hillside. Perpendicular shafts are then sunk from the top of the hill, connected with openings leading directly intothe top of the main horizontal shaft. By this arrangement the ore, when loosened in these perpendicular shafts, falls directly into the bins placed for its reception about the openings, or into the rows of cars in waiting to receive it. In this method dynamite and powder take the place of hand labor, the main mass of ore being dislodged and thrown into the shaft by blasting, instead of by hand labor.
But all these methods are overshadowed in magnitude by the great "open pit" systems, where the ore is taken from the surface and handled entirely by machinery, the only part played by the miner's pick being that of assisting in loosing certain fragments so that they may be more easily seized by the machines. Indeed, this system of mining partakes of the nature of quarrying rather than that of mining in the ordinary sense, the ore being scooped from the surface of the ground. One naturally thinks of a mine as being subterranean; but in the great open-pit mines in the Lake Superior region, which are the largest mines in the world, all the mining is done at the surface of the earth.
It should not be understood, however, that in such mines nature has left the red iron ore exposed at the surface in any great quantities. On the contrary, it is usually covered by a layer of earth ranging from a yard to ten or more yards in depth, and this, of course, must be removed before open-pit methods can be practised. Prospecting for such deposits is therefore just as necessary as in cases where the deposit is situated much deeper in the earth; and the business of prospectingby "test pit" men is as important an industry as ever.
When an available open-pit mine of sufficient extent has been located the gigantic task of "stripping" or removing the overlying layer of earth begins. Immense areas of land have been thus stripped in some of these undertakings, no difficulties being considered insurmountable. If a small river-bed lies in an unfavorable position, the course of the river is changed regardless of expense. Farms and farm houses are purchased and literally carted away, neither land nor houses representing values worth considering when compared with the stratum of ore beneath them. The single contract for stripping one area in the Lake Superior region was let for a sum amounting to half a million dollars.
As soon as a sufficiently large area has been stripped, railroads are constructed into the pit, steam shovels are run into place, and the actual work of mining begins. Five shovels full make a car-load, and under ordinary circumstances the five loads may be delivered in as many minutes.
The number of men required to manipulate one of these steam shovels is from ten to twelve. The ore itself is frequently so hard that the scoop of the shovel could not penetrate it until loosened and broken up, and it is the business of the gang of workmen to do this and slide the ore down within easy working distance of the shovel. This is mostly done by blasting with dynamite and powder, little of the actual labor being performed by hand. In blasting, a deep holeis first drilled into the ore near the top of the embankment, and into this hole a stick of dynamite is dropped and exploded. This enlarges the cavity sufficiently so that a quantity of blasting powder may be poured in and set off, tumbling the ore down within reach of the shovel.
This ore is frequently almost as hard as iron itself, many of the pieces thus dislodged being too large for convenient handling, either by the steam shovel or in the chutes at the wharves, and must be still further broken up. This is sometimes done by the men with picks; but in mining on a large scale, where the deposit is all of a very hard nature, crushing machines are used.
In this manner the steam shovel is kept constantly supplied with ore for the waiting train of cars. These trains are arranged on a track running parallel with the track from which the steam shovel operates, and at such a distance that the centre of the car will be directly under the opening in the bottom of the shovel when it is swung around on its crane. The engineer in charge of the locomotive drawing the train stops it in a position so that the first shovelful of ore will be dumped into the forward end of the first car. As each successive shovelful is deposited, representing about one-fifth of a car-load, the train is pulled or backed along the track about one-fifth of a car-length. In this manner it is only necessary for the steam shovel to be swung into the same position and dumped at the same point each time to insure the proper loading of the cars.
From what has been said it will be seen that in this open-pit mining the steam engine and steam locomotive still play a conspicuous part; but in the other forms of iron mining, electric or compressed-air motors are used, as much better adapted for underground work. In the Lake Superior region, where everything is done by the most modern methods, the use of horses and mules for hauling purposes is practically unknown.
The cars used for hauling the ore are of peculiar construction. The latest types are built of steel with a carrying capacity of fifty tons of ore, and are so made that by simply knocking loose a few pins their bottoms open and discharge the ore into the receiving bins on the wharves, or into the chutes leading to the waiting boats.
A perennial problem in iron mining, whether surface or subterranean, just as in all other kinds of mining, is the removal of accumulations of water, some of these mines filling at the rate of from twenty-five to thirty thousand gallons an hour. But an equally important problem is that of removing moisture from the ore itself. Obviously every additional pound of moisture adds to the cost and difficulty in handling, and inasmuch as this ore must be transported a distance of something like a thousand miles, necessitating three or four handlings in the process, the aggregate amount of wasted energy caused by each ton of water is enormous. It has been found that at least ten per cent of the moisture may be dried out of the ore before shipping, and that the ore does not tend to absorb moisture again under ordinary circumstances once it has been dried.This is of course of great advantage where it is found necessary to store it in heaps some little time before shipping.
In most industries, particularly where the percentage of waste products is large, it is found advantageous and economical to establish factories as near the source of supply of raw material as possible. But the iron ore mined in the Lake Superior region is transported something like a thousand miles before being delivered to the factories. The question naturally arises, Why is not the ore turned into pig iron or steel ingots at once as near the mouths of the mines as possible, and sent in this condensed form to the factories, thus saving more than half the cost of transportation? The answer is simple: the coal mines and steel factories lie in the East, one established by nature, the other by man many years before iron ore was found in the Lake region. And it is found just as cheap and easy to transport the iron to the coal regions as it would be to transport the coal to the ore regions. Furthermore, the factories in the neighborhood of Pittsburg and along the southern shores of Lake Erie and Lake Ontario are near the great centres of civilization, and are accessible the year round; while the Lake Superior region is "frozen in" for at least three months in the year.
And so, in place of a great traffic of coal westward to the Lake Superior regions, there is a great eastward traffic of ore, by rail and water, passing from themines to furnaces and factories a thousand miles away. Indeed, this is probably the greatest and most remarkable system of transportation in the world. Specially constructed trains, wharves, boats, and machinery, used for this single purpose, and not duplicated either in design or extent, make this stupendous enterprise a unique, as well as a purely American one.
The transportation begins with the train loads of ore that run from the mines to the lake shore and out upon the wharves built to receive them. These wharves are enormous structures, sometimes half a mile in length, built up to about the height of the masts of ore boats. On the sides and in the centres of these towering structures are huge bins for holding the ore, these bins communicating directly with the holds of the ore steamers tied up alongside. Four tracks are frequently laid on the top of the wharves, and are so arranged that trains four abreast can dump the ore into the bins, or waiting ships, at the same time. If the bins are empty and boats waiting to receive a cargo, the ore is discharged by long chutes into the holds from the cars. Otherwise the bins are filled, the trains returning to the mines as quickly as possible for fresh loads.
The boats for receiving this cargo are of special design, many of them differing very greatly in appearance from ordinary ocean liners of corresponding size. This is particularly true of the "whale-backs" which have little in common in appearance with ordinary steamers except in the matter of funnels; and even these are misplaced sternwards to a distance quite out of drawing with the length of the hull. Their shape isthat of the ordinary type of submarine boat—that is, cigar-shaped—this effect being obtained by a curved deck completely covering the place ordinarily occupied by a flat deck. A wheel-house, like a battle-ship's conning-tower, is placed well forward, supported on steel beams some distance above the curved deck for observation purposes; and engines, boilers, and coal bunkers occupy a small space in the stern. The boat, therefore, is mostly hold.
But the "whale-backs" form only a small portion of the ore-fleet. The ordinary type of boat conforms more nearly to the shape of ocean boats, except that the bridge, wheel-house, and engines are located as in the whale-backs. The bows of these boats are blunt, the desideratum in such craft being hull-capacity rather than speed. For sea-worthiness they are equal to any ocean boats, as the battering waves of Lake Superior are quite as powerful and even more treacherous than those of the Atlantic or Pacific. Some of these boats are five hundred feet long, equal to all but the largest ocean vessels. Their coal-carrying capacity is relatively small, since coaling stations are numerous at various points on the journey, and every available inch of space is utilized for the precious iron ore.
In order to facilitate loading, the decks are literally honey-combed with hatches, some boats having fifteen or sixteen openings extending the width of the deck. By this arrangement the time of loading is reduced to a matter of a few hours, as a dozen chutes, each discharging several tons of ore per minute, soonfill the yawning compartments with the necessary six, eight, or nine thousand tons, that make up the cargo.
Quite recently lake-navigators have learned, what rivermen have long known, that cheap transportation may be effected on a large scale by barges and towing. Before the outbreak of the Civil War forty years ago, the Mississippi river swarmed with great cargo-carrying steamers, employing armies of men and consuming enormous quantities of fuel. But after the war the experiment was tried of hauling the cargoes on barges towed by tug boats, and this proved to be so much cheaper that the fleet of great river boats soon disappeared. In somewhat the same way the barge has come into use of late years in the ore-traffic, and the great ore-steamers now tow behind them one or two barges equal in carrying capacity to themselves. In this way three ships' cargoes of ore are transported a thousand miles by a score of men, a dozen on the steamer and three or four on each of the barges. The barges themselves are rigged as ships, and if necessary can shift for themselves by means of sails attached to their stubby masts. But these are used only on special and unusual occasions, as in case of accidental parting of the hawsers during a storm.
The problem of loading the ships at the ore wharves is a simple one as compared with the equally important one of transferring the ore from the hold to trains of cars in waiting at the eastern end of the water route. For four handlings of the ore are necessary before it is finally deposited in the furnaces inthe east. The first of these is from the mine to cars; the second from the cars to the boats; the third from the boats to cars; and the fourth from the cars to the blast furnaces.
For many years about the only hand work done in any of these processes was that of transferring from the boats to the ore-trains, and even here "automatic unloaders" are now rapidly supplanting the tedious hand method. By the older methods a travelling crane, or swinging derrick, dropped a bucket into the hold of the ore-vessel, where workmen shovelled it full of the red ore. It was then lifted out by machinery and the contents dumped into cars in much the same manner as that of the steam shovel in the mines. Recently, however, a machine has been perfected which scoops up the ore from the ship's hold and transfers it to the cars without the aid of shovellers. The only human aid given this gigantic machine is to guide it by means of controlling levers—to furnish brains for it, in short—the "muscle" being furnished by steam power. The great arm of this automatic unloader, resembling the sweep of the old-fashioned well in principle, moves up and down, burying the jaws of the shovel into the ore in the hold, and pulling them out again filled with ore, with monotonous regularity, quickly emptying the vessel under the guidance of half a dozen men, and performing the labor of hundreds.
Thus the last field of activity for the laborer and his shovel, in the iron-ore industry, has been usurped by mechanical devices. From the time the ore is takenfrom the mine until it appears as molten metal from the furnaces, it is not touched except by mechanisms driven by steam, compressed air, or electricity. And yet, so rapid is the growth of the iron and steel industry that there is almost always a demand for more workmen.
For this reason, and perhaps because of the "American spirit" among workmen, innovations in the way of labor-saving machinery are not resisted among the mine laborers. The American workman seldom resists or attacks machinery on the ground that it "throws him out of a job," as does his English cousin. It would be unjust to attribute this attitude to superior acumen on the part of the American workman, and it is probably a difference in conditions and surroundings that accounts for the diametrically opposite views held by laborers on the two sides of the Atlantic. But after all, results must speak for themselves, and the advantage all lies in favor of the progressive attitude of the western laborer, if we may judge by the relative social status and financial standing of European and American workmen.
Since steel is a compound substance composed essentially of two elementary substances in varying proportions, it appears that the name "steel," like wood, refers to a class of which there are several varieties. This, of course, is the case, but for the moment we may consider steel as a single substance composed chiefly of iron and containing a certain percentage ofcarbon. In this respect it resembles cast iron, steel having a smaller amount of carbon. Wrought iron, on the other hand, contains no carbon at all, or at least only a trace of it. But whatever the ultimate destiny of iron ore—whether it is to become aristocratic manganese steel, or plebeian cast iron—it must first pass through certain processes before being "converted."
To extract the pure iron from the iron ore it is necessary to heat the ore in a furnace containing a certain quantity of coal, coke, or charcoal, and limestone. The furnaces used in this process are known as blast-furnaces, and in these about one ton of iron is extracted for every two tons of Lake Superior ore, one and a quarter tons of coke, and half a ton of limestone used. These quantities are by no means constant, of course, but they may be taken as representing roughly the relative amounts of material that must be fed into the furnaces.
Like everything else in the world of iron and steel, these blast-furnaces have undergone revolutionary improvements during the past quarter of a century. From being most dangerous and destructive structures causing frightful loss of life and producing only about one ton of iron a day for every man working about them, as formerly, they have now become relatively harmless monsters, capable of turning out six times that quantity of ore for each man employed.
The older blast-furnace was a huge, chimney-like structure, perhaps a hundred feet high, into which the ore, coal, and limestone were poured. Most of thework about these furnaces was done by manual labor, or at least manual labor was an active assistant to the machinery used in manipulating the furnaces. The top of the furnace was closed in by a great movable lid, or "bell," and the material for charging it was hauled up the sides by elevators and dumped in at the top. About the top of the furnace was constructed a staging upon which the workmen stood, an elevator shaft connecting the staging with the ground. The ore and other materials were brought to the foot of the shaft on cars from which it was shovelled into peculiarly designed wheelbarrows, trundled to the elevator, and hauled to the top.
In order to dump the wheelbarrow loads into the furnaces it was necessary to raise the bell. This was always dangerous, and frequently resulted in the suffocation or injury of the workmen on the staging. For when the bell was raised there was an escape of poisonous gases, which might flare out in a sheet of flame, with the possibility of burning or suffocating the workmen. The fumes from these gases, if inhaled in small quantities, might simply cause coughing, hiccoughing, or dizziness; but when inhaled in large quantities they struck down a man like the fumes of chloroform, suffocating him in a few seconds if he was not removed at once into a purer atmosphere. Indeed, the likelihood of this was so great that at many of these furnaces a special workman was detailed to take the position on the staging, well out of range of the gas, his sole duty being to rescue any of the men who might be overcome, and hurry them as quickly as possibledown the elevator shaft into the pure atmosphere below. It was not an uncommon thing in the neighborhood of these older furnaces to see stretched about on the ground at the base several workmen in various stages of suffocation. Fortunately, by use of precautionary measures, fatal accidents were rather unusual, the men being overcome only temporarily, and usually recovering quickly and returning to work.
But the poisonous gas coming from the top of the furnace was not the only, nor the worst, danger constantly menacing the men on the staging. Their greatest dread was the possibility of explosions occurring in the furnace, which might hurl the bell into the air and deluge the upper structure with molten metal. Against this possibility there was no safeguard in the older furnaces, explosions occurring without warning and frequently with terrible effects. But fortunately these older types of furnaces are being rapidly replaced by the newer forms in which the danger to life, at least from gas and explosions, is minimized. And even in the older furnaces, improvements in the structure of the bell and in methods of filling have greatly lessened the dangers.
In the modern type of blast-furnace the work at the top formerly performed by men on the staging is accomplished entirely by machinery. The general appearance of these furnaces is that of huge iron pipes or kettles mounted on several iron legs. The outer structure, or shaft, is constructed of plate iron, but this is lined with fire brick of considerable thickness, and may have a water jacket interposed between thesebricks and the shaft. About this large kettle are smaller kettles of somewhat similar shape having pipes leading from their tops to the larger structure. These smaller kettles are the "stoves" used in producing the hot air for the furnace.
The working capacity of some of these furnaces is in the neighborhood of a thousand tons of iron a day, although the average furnace produces only about half that quantity. The powerful machinery used for charging these monster caldrons hauls the ore and other charging materials to the top and dumps it in car-load lots.
In the older methods of manufacturing steel, the contents of the blast-furnaces were first drawn off into molds and allowed to cool into what is known as pig-iron. It was then necessary to re-heat this iron and treat it by the various methods for producing the kind of steel desired. By the newer methods, however, time and money are saved by converting the liquid iron from the blast-furnace directly into steel without going through the transitional stage of cooling it into pigs. Pigs of iron are still made in enormous quantities, to be sure, but mostly for shipment to distant places or for stores as stock material. For statistical purposes, however, the entire product of the blast-furnace, whether liquid or solid, is known as "pig iron."
The older method of removing the iron from the blast furnaces was by tapping at the opening near the bottom, the stream of liquid iron being allowed to flow into a connected series of sand molds, each mold being about three feet long by three or four incheswide. The bottom of these molds was flat but as the metal cooled in them the upper surface became round in shape, assuming a fanciful resemblance to a pig's back. In this molding a great amount of time was wasted in the slow process of cooling, and a large expenditure of energy wasted in this handling and re-handling of the metal.
In modern smelting works, however, pigs are no longer cast in sand molds, the molten metal from the furnace being discharged directly into iron molds attached to an endless chain. These molds are long, narrow, and shallow, having the general shape of sand molds. Each mold as it passes beneath the opening in the furnace remains just long enough to receive the requisite amount of metal to fill it, and then moves on to a point where it is either sprayed with water, or cooled by actually passing through a tank of water, emerging from this bath with the metal sufficiently solidified so that it may be dropped into a waiting car at the turning point of the endless chain. In this manner the charge from the blast-furnace may be drawn, cooled, and converted into pigs, loaded into cars, and hauled away without extra handlings or loss of time, the whole process occupying practically no more time than the initial step of tapping by the older method.
Where the contents of the blast-furnace are to be converted into steel at once, the molten metal is run off into movable tanks which carry it directly to the steel furnaces. These tanks, holding perhaps twenty tons of metal, are made of thick iron lined with firebrick, and arranged on low, flat cars designed specially for the purpose. These tanks are run under the spout of the furnace, filled with molten metal, and drawn to the steel works, possibly five miles away. As a rule, the distance is much less, but as far as the condition of the metal is concerned distance seems to make little difference, as even at the extreme distance there is no apparent cooling of the seething mass. The intense heat given off by these trains necessitates specially constructed cars, tracks, bridges, and crossings.
The destination of this train load of iron pots is the "mixer"—a great 200-ton kettle in which the products from the various furnaces are mixed and rendered uniform in quality. On the arrival of the train at the mixer, Titanic machinery seizes the twenty-ton pots and dumps their contents bodily into the glowing pool in the great crucible. Like the filling process, this operation occupies only a few minutes.
From the mixer the metal is poured out into ladles and transferred immediately to the "converter"—the important development of Sir Henry Bessemer's discovery that has made possible the modern steel industry. This converter resembles in shape some of the old mortars used in the American Civil War—barrel-shaped structures suspended vertically by trunnions at the middle and having an opening at the top. Into this opening at the top the metal from the mixer is poured and when the converter has been sufficiently charged a blast of cooled air is blown in at the bottom through the molten metal. This blast emerges atthe top as a long roaring flame, of a red color at first but gradually changing into white, and then faint blue. These changes in color are indicative of the changes that are taking place in the metal, and the appearance of a certain shade of color indicates that the conversion into steel is complete, and that it is time for shutting off the blast of air. Any mistake in this matter—even the variation of thirty seconds' time—means a loss of thousands of dollars in the quality of steel produced. The man whose duty it is to determine this important point, therefore, holds an exceptionally delicate and responsible position, and receives pay accordingly.
In deciding the exact moment when the blast shall be turned off, this workman is guided entirely by the sense of sight. Mounted on a platform commanding the best possible view of the mouth of the converter and wearing green glass goggles of special construction, this man watches the change of color in the flame until a certain shade is reached—a shade that to the ordinary untrained observer does not differ in appearance from that of a moment before—when he gives the signal to shut off the blast. When this signal is given the contents of the converter is no longer common-place cast iron, but steel, ready to be molded into rails, boilers, or a thousand and one other useful things.
The contents of the converter may now be drawn off as liquid steel into molds of any desired shape and size, and when cooled will be ready for shipment. But in the great steel factories the metal is not ordinarilyallowed to cool completely before being sent to the rolling mills, being drawn off into molds placed along the surface of small, flat cars. These molds are rectangular, ordinarily four or five feet high by less than two feet in diameter. The metal is poured into openings in the top of each mold, and allowed to cool, solidify, and to contract enough to permit the outer casings of the molds to be pulled off by machinery, leaving the glowing "ingots" of steel ready for molding by machinery in the mills.
The process just described is the one by which "Bessemer steel" is made. There is another important process in use, the "open hearth" method, which differs considerably from this; but before considering this process something more should be said of the man whose discoveries made possible the modern steel industry.
In the history of the progress of science and invention some one great name is usually pre-eminently associated with epoch-marking advances, although there may be a cluster of important but minor associates. This is true in the history of the modern steel industry, and the central name here is that of Sir Henry Bessemer.
Bessemer was born at Charlton, England, on Jan. 19, 1813. Always of an inventive turn of mind, his attention was first directed to improving the methods then in use for the manufacture of steel, while experimenting with the manufacture of guns. After severalyears of experimenting in his little iron works near London, he reached some definite results which he announced to the British Association in 1856. In this paper he described a process of converting cast iron into steel by removing the excess of carbon in the molten metal by a blast of air driven through it. This paper, in short, described the general principles still employed in the Bessemer process of manufacturing steel. And although the first simple process described by Bessemer has been modified and supplemented in recent years, it was in this paper that the process which placed steel upon the market as a comparatively cheap, and infinitely superior, substitute for ordinary iron, was first disclosed.
This famous paper before the British Association aroused great interest among the English ironmasters, and applications for licenses to use the new process were made at once by several firms. But the success attained by these firms was anything but satisfactory, although Bessemer himself was soon able to manufacture an entirely satisfactory product. The disappointed ironmasters, therefore, returned to the earlier processes, the inventor himself being about the only practical ironmaster who persisted in using it.
Recognizing the defects in his process, Bessemer set about overcoming them, and at the end of two years he had so succeeded in perfecting his methods that his product, equal in every respect to that of the older process, could be manufactured at a great saving of time and money. But the ironmasters were now skeptical, and refused to be again inveigled into applyingfor licenses. Bessemer, therefore, with the aid of friends, erected extensive steel works of his own at Sheffield, and began manufacturing steel in open competition with the other steel operators. The price at which he was able to sell his product and realize a profit was so much below the actual cost of manufacture by the older process, that there was soon consternation in the ranks of his rivals. For when it became known that the firm of Henry Bessemer & Co. was selling steel at a price something like one hundred dollars a ton less than the ordinary market price, there was but one thing left for the ironmasters to do—surrender, and apply for licenses to be allowed to use the new process.
By this means, and through the profits of his own establishment, Bessemer eventually amassed a well-earned fortune. Moreover, he was honored in due course by a fellowship in the Royal Society, and knighted by his government.
One other name is usually associated with that of Bessemer in the practical development of the inventor's original idea. That is the name of Robert Mushet, and the "Bessemer-Mushet" process is still in use. Mushet's improvement over Bessemer's original process was that of adding a certain quantity ofspiegeleisen, or iron containing manganese, which, for some reason not well understood, simplifies the process of steel making. Mushet, therefore, must be considered as the discoverer of a useful, though not an absolutely essential, accessory to the Bessemer process.
In the open-hearth method the metal from the blast-furnaces is not sent to the converter, but is poured into oven-like structures built of fire brick, and in these heated to a terrific temperature. This heat has the same effect upon the metal as the blast of air in the Bessemer converter, and this open-hearth process has become very popular for manufacturing certain kinds of steel. While in the method of application this process differs greatly from that of Bessemer, it differs largely in the fact that the oxygen necessary to burn off the carbonic oxide, silicon, etc., is made to play over the molten mass instead of passing through it.
It has been noted that the old type of blast-furnace gave off great quantities of combustible gases which became waste products. Even gases containing something like 20 or 25 per cent. of carbonic acid may be highly inflammable, and thus an enormous quantity of valuable fuel was constantly wasted. In some furnaces, to be sure, they were put to practical use for heating the blast, but as the quantities given off were greatly in excess of the amount necessary for this purpose, there was a constant loss even with such furnaces.
Quite recently it has been found that the gases can be used directly in gas engines, developing three or four times as much energy in this way as if they were used as fuel under ordinary steam boilers. These engines are now used for operating the rolling-mill machinery, and the machinery of shops adjoining thefurnaces, which, however, must not be situated at any very great distances from the furnaces. This accounts partly for the grouping together of blast-furnaces, rolling mills, and machine shops, the economical feature of this arrangement being so great that segregated establishments find it next to impossible to compete in the open market with such "communities" under the conditions prevailing in the steel industry.
The introduction of Krupp steel, or nickel, for armor plates, a few years ago, called attention in a popular way to the fact that for certain purposes pure steel—that is, iron plus a certain quantity of carbon—was not as useful as an alloy of steel with some other metal. An alloy was a great improvement over ordinary steel or iron plates used in warfare; but in the more peaceful pursuits, as well as in warfare, certain alloyed steels, such as chrome steel, tungsten steel, and manganese steel play a very important part.
Chrome steel, for example, in the form of projectiles, is the most dreaded enemy of nickel-steel armor plates, because of the hardness and elasticity of armor-piercing projectiles made of it. Such a steel contains about two per cent. of chromium with about one or two per cent. of carbon, which when suddenly cooled is extremely hard and tough. This kind of steel and manganese steel are the best guards against the burglar and safe-blower, as they resist even very highly tempered and hardened drills. As this steel is relativelycheap to manufacture, it is frequently used in the construction of safes and burglar-proof gratings. For this purpose, however, it is sometimes combined in alternate layers with soft wrought iron, the steel resisting the point of the drill, while the iron furnishes the necessary elasticity to resist the blows of the sledge. The bars used in modern jails and prisons are often made in a similar manner of alternate sheaths of iron and chrome steel. Against the time-honored "hack-saw," the bugbear of prison officials for generations, such bars an inch and a quarter in diameter offer an almost insurmountable obstacle; and they are equally effective against a heavy sledge hammer.
At least one case is recorded in which the use of these "composite" bars resulted in a disastrous fire in a prison. A small blaze having started in the basement of this prison, attempts to reach it with a stream of water were defeated by the bars of the steel gratings at the windows, which would not admit the nozzle of the hose. A corps of men armed with hack-saws, crow-bars, and sledges attacked this grating, which, if made of ordinary steel, could have been readily broken. But against these composite bars they produced no appreciable effect. Meanwhile the fire gained rapidly, threatening the building and its eight hundred inmates, and was only checked after holes had been made through fire-proof floors and ceilings for admitting the nozzle.
Manganese steel is peculiar in becoming ductile by sudden cooling, and brittle on cooling slowly—precisely the reverse of ordinary steel. It contains about1.50 per cent. of carbon, and about 12 per cent. of manganese. If a small quantity of manganese, that is, 1 or 2 per cent., is used the steel is very brittle, and becomes more so as greater quantities of the manganese are used, up to about 5 per cent. From that point, however, it becomes more ductile as the quantity of manganese is increased, until at about 12 per cent. it reaches an ideal state. When used for safes and money vaults this steel has one great advantage over chrome steel—it is not affected by heat. By using a blow-pipe and heating a limited area of steel, the burglar is able to "draw the temper" of ordinary steel to a sufficient depth so that he can drill a hole to admit a charge of dynamite; but manganese steel retains its temper under the blow-pipe no matter how long it may be applied. Against attacks of the sledge, however, it is probably inferior to chrome steel.
Like manganese steel, tungsten steel retains its temper even when heated to high temperatures. For this reason it is used frequently in making tools for metal-lathe work where thick slices of iron are to be cut, as even at red heat such a tool continues to cut off metal chips as readily as when kept at a lower temperature. This steel contains from 6 to 10 per cent. of tungsten, a metallic element with which we have previously made acquaintance in our studies of the incandescent lamp.
Notlong ago a little company of men met in a lecture hall of Columbia University to discuss certain questions in applied science. It was a small gathering, and its proceedings were so unspectacular as to be esteemed worth only a few lines of newspaper space. The very name—"Society of Electro-Chemistry"—seemed to mark it as having to do with things that are caviare to the general. The name seems to smack of fumes of the laboratory, far removed from the interests of the man in the street. Yet Professor Chandler said in his address of welcome to the members of the society, that though theirs was the very youngest of scientific organizations, he could confidently predict for it a future position outranking that of all its sister societies; and his prediction was based on the belief that electro-chemistry is destined to revolutionize vast and important departments of modern industry. A majority of the heat-using methods of mechanics will owe their future development to the new science.
In a word, then, despite itsrepellentname, the society in question has to do with affairs that are of the utmost importance to the man in the street. Though its members may sometimes deal in occult formulasand abstruse calculations, yet the final goal of their studies has to do not with abstractions but with practicalities,—with the saving of fuel, the smelting of metals, the manufacture of commodities. But theory in the main must precede practice—the child creeps before it walks. "The later developments of industrial chemistry," says Sir William Ramsey, "owe their success entirely to the growth of chemical theory; and it is obvious," he adds significantly, "that that nation which possesses the most competent chemists, theoretical and practical, is destined to succeed in the competition with other nations for commercial supremacy and all its concomitant advantages."
Fortunately this interdependence of science and industry is not a mere matter of prophecy—for the future tense is never quite so satisfying as the present. Vastly important changes have already been accomplished; old industries have been revolutionized, and new industries created. The commercial world of to-day owes vast debts to the new science. Professor Chandler outlined the character of one or two of these in the address just referred to. He cited in some detail, for example, the difference between old methods and new in such an industry as the manufacture of caustic soda. He painted a vivid word picture of the distressing conditions under which soda was produced in the old-time factories. Salt and sulphuric acid were combined to produce sulphate of soda, which was mixed with lime and coal and heated in a reverberatory furnace. Each phase of the process was laborious. The workmen operating the furnacessweltered all day long in an almost unbearable atmosphere—stripped to the waist, dripping with perspiration, sometimes overcome with heat. Their task was one of the most trying to which a man could be subjected.
But to-day, in such establishments as the soda manufactories at Niagara Falls, all this is changed. A salt solution circulates continuously in retorts where it can be acted upon by electricity supplied from dynamos operated by the waters of the Niagara River. The workmen, comfortably dressed and moving about in a normal temperature, have really nothing to do but refill the retorts now and then and remove the finished product. "It almost seems," Professor Chandler added with a smile, "as if workmen ought to be glad to pay for the privilege of participating in so pleasant an occupation. At all events it is, in all seriousness, a pleasure for the visitor who knows nothing of old practices to witness this triumph of a modern scientific method."
Even more interesting, said Professor Chandler, are the processes employed in the modern method of producing the metal aluminum by the electrolytic process. The process is based on the discovery made by Mr. Charles M. Hall while he was a student working in a college laboratory, that the mineral cryolite will absorb alumina to the extent of twenty-five per cent. of its bulk, as a sponge absorbs water. The solution of this compound is then acted on by electricity, and the aluminum is deposited as pure metal. A curiously interesting practical detail of the process is based on the fact that pulverized coke remains perfectly dry andrises to the surface when stirred into a crucible containing the hot alumina solution: moreover, it rises to the surface and remains there as a shield to protect the workmen against the heat of the solution. It serves yet another purpose, as the powdered alumina may be sifted upon it and left there to dry before being stirred into the crucible. A most ingenious yet simple device tells the workman when any particular crucible is in need of replenishing. A small, ordinary, incandescent electric-light bulb is placed in circuit between the poles that convey the electric current through the alumina solution. So long as the crucible contains alumina, the bulb does not glow, because twenty volts of electricity are required to make it incandescent, whereas seven volts pass through the solution. But so soon as the alumina becomes exhausted, resistance to the current rises in the cryolite solution and, as it were, dams back the electric current until it overflows into the wire at sufficient pressure to start the signal lamp. Then it is necessary merely for a workman to stir into the solution the dry alumina resting on the surface, along with the coke that supports it. This, of course, reestablishes the electrolytic process; the lamp goes out and the coke, unaffected by its bath, rises to the surface to support a fresh supply of alumina.
Such a process as this, contrasted with the usual methods of smelting metals in fiercely heated furnaces, seems altogether wonderful. Here a pure metal is extracted from the clayey earth of which it formed a part, without being melted or subjected to any of the familiar processes of the picturesque, but costly, laborious, andeven dangerous, blast-furnaces. There is no glare and roar of fires; there are no showers of sparks; there is no gush of fiery streams of molten metal. A silent and invisible electric current, generated by the fall of distant waters, does the work more expeditiously, more efficiently, and more cheaply than it could be done by any other method as yet discovered.
Fully to appreciate the importance of the method just outlined, we must reflect that aluminum is a metal combining in some measure the properties of silver, copper, and iron. It rivals copper as a conductor of electricity; like silver it is white in color and little subject to tarnishing; like iron it has great hardness and tensile strength. True, it does not fully compete with the more familiar metals in their respective fields; but it combines many valuable qualities in fair degree; and it has an added property of extreme lightness that is all its own. Add to this the fact that aluminum is extremely abundant everywhere in nature—it is a constituent of nearly all soils and is computed to form about the twelfth part of the entire crust of the earth—whereas the other valuable metals are relatively rare, and it will appear that aluminum must be destined to play an important part in the mechanics of the future. There is every indication that the iron beds will begin to give out at no immeasurably distant day; but the supply of aluminum is absolutely inexhaustible. Until now there has been no means known of extracting it cheaply from the clay of which it forms so important a constituent. But at last electro-chemistry has solved the problem; and aluminum is sure to takean important place among the industrial metals, even should it fall short of the preeminent position as "the metal of the future" that was once prematurely predicted for it.