Kitabı oku: «Inventions in the Century», sayfa 22
CHAPTER XXIII.
LEATHER
It is interesting to speculate how prehistoric man came to use the skin of the beasts of the field for warmth and shelter. Originally no doubt, and for untold centuries, the use was confined to the hairy, undressed, fresh, or dried skins, known as pelts. Then came the use of better tools. The garments have perished, but the tools of stone and of bronze survived, which, when compared with those employed among the earliest historic tribes of men, were found to be adapted to cut and strip the hairy covering from the bodies of animals, and clean, pound, scrape and otherwise adapt them to use.
And ever since the story of man began to be preserved in lasting records from farthest Oriental to the northernmost limits of Europe and America, memorials of the early implements of labour in the preparation of hides for human wear have been found. The aborigines knew how to sharpen bones of the animals they killed to scrape, clean, soften or roughen their skins. They knew how to sweat, dry, and smoke the skins, and this crude seasoning process was the forerunner of modern tanning. But leather as we know it now, that soft, flexible, insoluble combination of the gelatine and fibrine of the skin with tannic acid, producing a durable and imputrescible article, that will withstand decay from the joint attack of moisture, warmth and air, was unknown to the earlier races of men, for its production was due to thorough tanning, and thorough tanning was a later art.
When men were skin-dressed animals they knew little or nothing of tanning. Tannic acid is found in nearly every plant that grows, and its combination with the fresh skins spread or thrown thereon, may have given rise to the observation of the beneficial result and subsequent practice. But whether discovered by chance, accident or experience, or invented from necessity, the art of tanning should have rendered the name of the discoverer immortal. The earliest records, however, describe the art, but not the inventor.
From the time the Hebrews covered the altars of their tabernacles with rams' skins dyed red, as recorded in Exodus; when they and the Egyptians worked their leather, currying and stretching it with their knives, awls, stones, and other implements, making leather water buckets, resembling very much those now made by machinery, covering their harps and shields with leather, ornamental and embossed; from the days of the early Africans, famous for their yellow, red and black morocco; from the days of the old national dress of the Persians with their leather trousers, aprons, helmets, belts and shirts; from the time that the ancient Scythians utilised the skins of their enemies, and Herodotus described the beauty and other good qualities of the human hide; from the early days of that peculiar fine and agreeable leather of the Russians, fragrant with the oil of the birch; from the days of the white leather of the Hungarians, the olive-tanned leather of the Saracens; from the time of the celebrated Cordovan leather of the Spaniards; from the ancient cold periods of the Esquimaux and the Scandinavians, who, clad in the warm skins of the Arctic bears, stretched tough-tanned sealskin over the frame work of their boats; from the time of the introduction of the art of the leather worker to the naked Briton, down to almost the nineteenth century, substantially the same hand tools, hard hand labour, and the old elbow lubricant were known and practised.
Hand tools have improved, of course, as other arts in wood and iron making have developed, but the operations are about the same. There were and must be fleshing knives to scrape from off the hide the adherent flesh and lime, – for this the hide is placed over the convex edge of an inclined beam and the work is called beaming; the curriers' knife for removing the hair; skiving, or the cutting off the rough edges and fleshy parts on the border of the hide; shaving and flattening; the cutting away of the inequalities left after skiving; stoning, the rubbing of the leather by a scouring stone to render it smooth; slicking, to remove the water and grease; or to smooth and polish, by a rectangular sharpened stone, steel or glass tool; whitening, to shave off thin strips of the flesh, leaving the leather thinner, whiter and more pliable; stuffing, to soften the scraped and pounded hides and make them porous; graining, the giving to the hair or grain side a granular appearance by rubbing with a grooved or roughened piece of wood; bruising or boarding to make the leather supple and pliable by bringing the two flesh sides together and rubbing with a graining board; scouring, by aid of a stream of water to whiten the leather by rubbing with a slicking stone or steel.
The inventions of the century consist in labour-saving machinery for these purposes, new tanning and dressing processes, and innumerable machines for making special articles of leather.
As before stated, the epoch of modern machinery commenced with the practical application of water power to other than grinding mills, and of steam in place of water, contemporaneously with the invention of spinning and weaving machinery in the last half of the eighteenth century. These got fairly to work at the beginning of the century, and the uses of machinery spread to the treatment of leather. John Bull was the appropriate name of the man who first patented a scraping machine in England, about 1780, and Joseph Weeks the next one, some years later.
One of the earliest machines of the century was the hide mill, which, after the hand tools had scraped and stoned, shaved and hardened the hides, was used to rub and dub them, and soften and swell them for tanning. Pegged rollers were the earliest form for this purpose, and later corrugated rollers and power-worked hammers were employed. Hundreds of hides could be softened daily by these means.
Then came ingenious machines to take the place of the previous operations of the hand tools, – the fleshing machine, in one form of which the hides are placed on a curved bed, and the fleshy parts scraped off or removed by revolving glass blades, or by curved teeth of steel and wood in a roller under which a table is given a to-and-fro movement; tanning apparatus of a great variety, by which hides, after they are thoroughly washed and softened, and the pores opened by swelling, are subjected to movements in the tanning liquor vats, such as rocking or oscillating, rotary, or vertical; or treated by an air exhaust, known as the vacuum process; in all of which the object is to thoroughly impregnate in the shortest time all the interstices and pores of the skin with the tannic acid, by which the fibrous and gelatinous matter is made to combine to form leather, and by which process, also, the hide is greatly increased in weight.
Reel machines are then employed to transfer the hides from one vat to another, thus subjecting them to liquors of increasing strength. Soaking in vats formerly occupied twelve or eighteen months, but under the new methods the time has been greatly reduced. And now since 1880, the chemists are pushing aside the vegetable processes, and substituting mineral processes, by which tanning is still further shortened and cheapened. The new processes depend chiefly on the use of chromium compounds.
Then came scouring machines, in which a rapidly revolving stiff brush is used to scour the grain or hair side, removing the superfluous colouring matter, called the bloom, and softening and cleansing the hide; the slicking or polishing machines to clean, stretch and smooth the leather by glass, stone, or copper blades on a rapidly-moving belt carried over pulleys; whitening, buffing, skiving, fleshing and shaving machines, all for cutting off certain portions and inequalities of the leather, and reducing its thickness.
In one form of this class of machines an oscillating pendulum lever is employed, carrying at its end a revolving cylinder having thirty or more spiral blades. The pendulum swings to and fro at the rate of ninety movements a minute, while the cylinder rolls over the leather at the rate of 2780 revolutions per minute. Scarfing, skiving, chamfering, bevelling, feather-edging, appear to be synonymous terms for a variety of machines for cutting the edges of leather obliquely, for the purpose chiefly of making lap seams, scarf-joints, and reducing the thickness and stiffness of leather at those and certain other points.
Then there are leather-splitting machines, consisting of one or more rollers and a pressure bar, which draw and press the leather against a horizontally arranged and adjustable knife, which nicely splits the leather in two parts, and thus doubles the quantity. This thin split leather is much used in making a cheap quality of boots and shoes and other articles.
There are also corrugating, creasing, fluting, pebbling, piercing and punching machines; machines for grinding the bark and also for grinding the leather; machines for gluing sections of leather together, and machines for sewing them; machines for rounding flat strips of leather, for the making of whips and tubes; machines for scalloping the edges; and a very ingenious machine for assorting leather strips or strings according to their size or thickness.
The most important improvements of the century in leather working relate to the manufacture of boots and shoes. It could well be said of boots and shoes, especially those made for the great mass of humanity, before the modern improvements in means and processes had been invented: "Their feet through faithless leather met the dirt."
It is true that in the eighteenth century, both in Europe and America, the art of leather and boot and shoe making had so far advanced that good durable foot wear was produced by long and tedious processes of tanning, and by careful making up of the leather into boots and shoes by hand; the knife, the awl, the waxed thread, the nails and hammer and other hand tools of the character above referred to being employed. But the process was a tedious and costly one and the articles produced were beyond the limits of the poor man's purse. Hence the wooden shoes, and those made of coarse hide and dressed and undressed skins, and of coarse cloth, mixed or unmixed with leather.
In 1809, David Mead Randolph of England patented machinery for riveting soles and heels to the uppers instead of sewing them together.
The celebrated civil engineer, Isambard M. Brunel, shortly thereafter added several machines of his own invention to Randolph's method, and he established a large manufactory for the making chiefly of army shoes. The various separate processes performed by his machines involved the cutting out of the leather, hardening it by rolling, securing the welt on to the inner sole by small nails, and studding the outer sole with larger nails. Divisions of men were employed to work each separate step, and the shoes were passed from one process to another until complete.
Large quantities of shoes were made at reduced prices, but complaints were made as to the nails penetrating into the shoe and hurting the feet. The demand for army shoes fell off, and the system was abandoned; but it had incited invention in the direction of machine-made shoes and the day of exclusive hand labour was doomed.
About 1818 Joseph Walker of Hopkinston, Massachusetts invented the wooden peg. Making and applying pegs by hand was too slow work, and machines were at once contrived for making them. As one invention necessitates and begets others, so special forms of machines for sawing and working up wood into pegs were devised.
Such machinery was for first sawing the selected log of wood into slices across the grain a little thicker than the length of a peg and cutting out knots in the wood; then planing the head of the block smooth; grooving the block with a V-shaped cutting tool; splitting the pegs apart, and then bleaching, drying, polishing and winnowing them.
It took forty or fifty years to perfect these and kindred machines, but at the end of that time there was a factory at Burlington, Vermont, which from four cords of wood, made every day four hundred bushels of shoe pegs.
About 1858 B. F. Sturtevant of Massachusetts made a great improvement in this line. He was a very poor man, getting a living by pegging on the soles of a few pair of shoes each day. He devised a pegging machine, and out of his scanty earnings and at odd hours, with much pain and labour, and by borrowing money, he finally completed it. The machine made what was called "peg wood," a long ribbon strip of seasoned wood, sharpened on one edge and designed to be fed into the machine for pegging shoes. The shoes were punctured by awls driven by machinery, and then as the peg strip was carried to it the machine severed the strip into chisel-edged pegs, and peg-driving mechanism drove them into the holes. Nine hundred pegs a minute were driven. It soon almost supplanted all other peg-driving machines, and after the machines were quite generally introduced, there were made in one year alone in New England fifty-five million pairs of boots and shoes pegged by the Sturtevant machines.
Other forms of pegs followed, such as the metal screw pegs, and machines to cut them off from a continuous spiral wire from which they were made. Lasts on which the shoes were made had been manufactured by the hundred thousand on the wood-turning lathes invented by Blanchard, described in the chapter on Wood-Working.
In 1858 also, about the same time the Sturtevant pegging machine was introduced, the shoe-sewing machine was developed. The McKay Shoe-Sewing Machine Co. of Massachusetts after an expenditure of $130,000, and three years' time in experiments, were enabled to put their machines in practical operation. The pegging machines and sewing machines worked a revolution in shoemaking.
A revolution in the art of shoemaking thus started was followed up by wondrous machines invented to meet every part of the manufacture. Lasting machines for drawing and fitting the leather over lasts, in which the outer edges of the leather are drawn over the bottom of the last and tacked thereto by the hands and fingers of the machine instead of those of the human hand, were invented.
Indenting machines: – The welt is known as that strip of leather around the shoe between the upper and the sole, and machines were invented for cutting and placing this, indenting it for the purpose of rendering it flexible and separating the stitches, all a work until recently entirely done by hand. Machines for twining the seams in the uppers, and forming the scallops; machines especially adapted to the making of the heel, as heel trimming and compressing, rounding and polishing, and for nailing the finished heel to the boot or shoe; machines for treating the sole in every way, rolling it, in place of the good old way of pounding it on a lap stone; trimming, rounding, smoothing, and polishing it; machines for cutting out gores; machines for marking the uppers so that at one operation every shoe will be stamped by its size, number, name of manufacture, number of case, and any other convenient symbols; machines for setting the buttons and eyelets; all these are simply members in the long line of inventions in this art.
The old style of boot has given way to the modern shoe and gaiter, but for the benefit of those who still wear them, special machines for shaping the leg, called boot trees, have been contrived.
So far had the art advanced that twenty years ago one workingman with much of this improved machinery combined in one machine called the "bootmaker," could make three hundred pairs of boots or shoes a day. Upward of three thousand such machines were then at work throughout the world; and one hundred and fifty million pairs of boots were then being made annually thereon. Now the number of machines and pairs of boots and shoes has been quadrupled.
And the world is having its feet clothed far more extensively, better and at less cost than was ever possible by the hand system. The number of workers in the art, both men and women, has vastly increased instead of being diminished, while their wages have greatly advanced over the old rates.
As an illustration of how rapidly modern enterprise and invention proceeds in Yankeeland, it has been related that some years ago in Massachusetts, after many of these shoe-making machines had got into use, a factory which was turning out 2400 pairs of shoes every day was completely destroyed by fire on a Wednesday night. On Thursday the manufacturer hired a neighbouring building and set carpenters at work fitting it up. On Friday he ordered a new and complete outfit of machinery from Boston; on Saturday the machinery arrived and the men set it up; on Monday work was started, and on Tuesday the manufacturer was filling his orders to the full number of 2400 pairs a day.
There are very many people in the world who still prefer the hand-made shoe, and there is nothing to prevent the world generally from going back to that system if they choose; but St. Crispin's gentle art has blossomed into a vaster field of blessings for mankind under the fruitful impetus of invention than if left to vegetate under the simple processes of primitive man.
Horses, no less than man, have shared in the improvement in leather manufacture. The harnesses of the farmer's and labouring man's horses a century ago, when they were fortunate enough to own horses, were of the crudest description. Ropes, cords, coarse bands of leather were the common provisions. Now the strength and cheapness of harnesses enable the poor man to equip his horse with a working suit impossible to have been produced a hundred years ago.
To the beautiful effects produced by the use of modern embossing machines on paper and wood have been added many charming patterns in embossed leather. Books and leather cases, saddlery and household ornamentation of various descriptions have been either moulded into forms of beauty, or stamped or rolled by cameo and intaglio designs cut into the surface of fast-moving cylinders.
The leather manufactures have become so vastly important and valuable in some countries, especially in the United States – second, almost to agricultural products – that it would be very interesting to extend the description to many processes and machines, and to facts displaying the enormous traffic in leather, now necessarily omitted for want of space.
CHAPTER XXIV.
MINERALS – WELLS
Dost thou hear the hammer of Thor,
Wielded in his gloves of iron?
As with leather, so with stone, the hand tools and hard labour have not changed in principle since the ancient days. The hammer for breaking, the lever for lifting, the saw for cutting, rubbing-stones and irons for smoothing and polishing, sand and water for the same purpose, the mallet and chisel, and other implements for ornamenting, the square, the level, and the plumb for their respective purposes, all are as old as the art of building.
And as for buildings and sculpture of stone and marble made by hand tools, we have yet to excel the pyramids, the Parthenon of Athens, which "Earth proudly wears as the best gem upon her zone," the palaces, coliseums, and aqueducts of Rome, the grand and polished tombs of India, the exquisite halls of the Alhambra, and the Gothic cathedrals.
But the time came when human blood and toil became too dear to be the possession solely of the rulers and the wealthy, and to be used alone to perpetuate and commemorate riches, power and glory.
Close on the expansion of men's minds came the expansion of steam and the development of modern inventions. The first application of the steam engine in fields of human labour was the drawing of water from the coal mines of England; then in drawing the coal itself.
It was only a step for the steam engine into a new field of labour when General Bentham introduced his system of wood-sawing machinery in 1800; and from sawing wood to sawing stone was only one more step. We find that taken in 1803 in Pennsylvania, when Oliver Evans of Philadelphia drove with a high-pressure steam engine, "twelve saws in heavy frames, sawing at the rate of one hundred feet of marble in twelve hours." How long would it have taken hand sawyers of marble at ancient Paros and Naxos to have done the same?
Stone-cutting machines of other forms than sawing then followed.
It was desired to divide large blocks generally at the quarries to facilitate transportation. Machines for this purpose are called stone-channelling machines. They consist of a gang of chisels bound together and set on a framework which travels on a track adjacent to the stone to be cut, and so arranged that the cutters may be set to the stone at desired angles, moved automatically forward and back in the grooves they are cutting, be fed in or out, raised or lowered, detached, and otherwise manipulated in the operation.
Other stone-cutting machines had for their objects the cutting and moulding the edges of tables, mantels and slabs; and the cutting of circular and other curved work. In the later style of machine the cutter fixed on the end of a spindle is guided in the desired directions on the surface of the stone by a pointer, which, attached to the cutter spindle, moves in the grooves of a pattern also connected to the rotating support carrying the cutter.
Other forms of most ingenious stone-dressing and carving machines have been devised for cutting mouldings, and ornamental figures and devices, in accordance with a model or pattern fixed to the under side of the table which carries the stone or marble to be dressed; and in which, by means of a guide moving in the pattern, the diamond cutter or cutters, carried in a circular frame above the work and adjusted to its surface, are moved in the varying directions determined by the pattern. A stream of water is directed on the stone to clear it of the dust during the operations. The carving of stone by machinery is now a sister branch of wood carving. Monuments, ornamentation, and intricate forms of figures and characters are wrought with great accuracy by cutting and dressing tools guided by the patterns, or directed by the hand of the operator.
For the dressing of the faces of grindstones, special forms of cutting machines have been devised.
It was a slow and tedious task to drill holes through stone by hand tools; and it was indeed a revolution in this branch of the art when steam engines were employed to rotate a rod armed at its end with diamond or other cutters against the hardest stone. This mode of drilling also effected a revolution in the art of blasting. Then, neither height, nor depth, nor thickness of the stone could prevent the progress of the drill rod. Tunnels through mountain walls, and wells through solid quartz are cut to the depth of thousands of feet.
One instance is related of the wonderful efficiency on a smaller scale of such a machine: The immense columns of the State Capitol at Columbus, Ohio, were considered too heavy for the foundation on which they rested. The American Diamond Rock Boring Company of Providence, Rhode Island, bored out a twenty-four inch core from each of the great pillars, and thus relieved the danger.
In the most economical and successful stone drills compressed air is employed as the motive power to drive the drills, which may be used singly or in gangs, and which may be adjusted against the rock or quarry in any direction. When in position and ready for work a few moments will suffice to bore the holes, apply the explosive and blast the ledge. The cleaning away of submarine ledges in harbours, such as the great work at Hell Gate in the harbour of New York, has thus been effected.
Crushing: – Among the most useful inventions relating to stone working are machines for crushing stones and ores, and assorting them. The old way of hammering by hand was first succeeded by powerful stamp hammers worked by steam. Both methods of course are still followed, but they demand too great an expenditure of force and time.
About a third of a century ago, Eli Whitney Blake of New Haven, Connecticut, was a pioneer inventor of a new and most successful type of stone breaking machine, which ever since has been known as the "Blake Crusher." This crusher consists of two ponderous upright jaws, one fixed and the other movable, between which the stones or ores to be crushed are fed. Each of the jaws is lined with the hardest kind of chilled steel. The movable jaw is inclined from its lower end from the fixed jaw and at its upper end is pivoted to swing on a heavy round iron bar. The movable jaw is forced toward the fixed jaw by two opposite toggle levers set, in one form of the crusher, at their inner ends in steel bearings of a vertical vibrating, rocking lever, one of the toggles bearing at its outer end against the movable jaw and the outer toggle against a solid frame-work. The rocking lever is operated through a crank by a steam engine, and as it is vibrated, the toggle joint forces the lever end of the movable jaw towards the fixed jaw with immense force, breaking the hardest stone like an eggshell.
The setting of the movable jaw at an incline enables the large stone to be first cracked, the movable jaw then opens, and as the stone falls lower between the more contracted jaws, it is broken finer, until it is finally crushed or pulverized and falls through at the bottom. The movable jaw is adjustable and can be set to crush stones to a certain size.
As the rock drill made a revolution in blasting and tunnelling, so the Blake crusher revolutionised the art of road making. "Road metal," as the supply of broken stones for roads is now called, is the fruit of the crusher. Hundreds of tons of stone per day can be crushed to just the size desired, and the machine may be moved from place to place where most convenient to use.
Other crushers have been invented, formed on the principle of abrasion. The stones, or ore, fall between two great revolving disks, having corrugated steel faces, which are set the desired distance apart, and between which the stones are crushed by the rubbing action. In this style of machine the principle of a gradual breaking from a coarse to a finer grade, is maintained by setting the disks farther apart at the centre where the stone enters, and nearer together at their peripheries where the broken stone is discharged. Large smooth or corrugated rollers, conical disks, concentric rollers armed with teeth of varying sizes, and yet so arranged as to preserve the feature of the narrowing throat at the bottom or place of discharge, have also been devised and extensively used.
A long line of inventions has appeared especially adapted to break up and separate coal into different sizes. To view the various monstrous heaps of assorted coals at the mouth of a coal mine creates an impression that some great witch had imposed on a poor victim the gigantic and seemingly impossible task of breaking and assorting a vast heap of coal into these separate piles within a certain time – a task which also seems to have been miraculously and successfully performed within such an exceedingly short time as to either satisfy or confuse the presiding evil genius.
Modern civilisation has been developed mostly from steam and coal, and they have been to each other as strong brothers, growing more and more mutually dependent to meet the demands made upon them.
The mining of coal, and its subsequent treatment for burning, before the invention of the steam engine, were long, painful, and laborious tasks, and the steam engine could never have had its modern wants supplied if its power had not been used to supplement, with a hundredfold increased effect, the labour of human hands.
It being impracticable to carry steam or the steam engine to the bottom of the mine for work there, compressed air is there employed, which is compressed by a steam engine up at the mouth. By this compressed air operated in a cylinder to drive a piston, and a connecting rod and a pick, a massive steel pick attached to the rod may be driven in any direction against the wall of coal at the rate of from ninety to one hundred and twenty blows per minute; and at the same time the discharged compressed, cold, pure, fresh air flows into and through the mine, affording ventilation when and where most needed.
In addition to these great drills, more recent inventors have brought out small machines for single operators, worked by the electric motor.
After the coal is lifted out, broken and assorted, it needs to be washed free of the adhering dust and dirt; and for this purpose machines are provided, as well as for screening, loading and weighing. The operations of breaking, assorting and washing are often combined in one machine, while an intermediate hand process for separating the pieces of slate from the coal may be employed; but additional automatic means for separating the coal and slate are provided, consisting in forcing with great power water through the coal as it falls into a chamber, which carries the lighter slate to the top of the chamber, where it is at once drawn off.
The chief of machines with ores is the ore mill, which not only breaks up the ore but grinds or pulverises it.
Some chemical and other processes for reducing ores have been referred to in the Chapter on Metallurgy.
Other mechanical processes consist of separators of various descriptions – a prominent one of which acts on the principal of centrifugal force. The crushed material from a spout being led to the centre of a rapidly rotating disk is thrown off by centrifugal force; and as the lighter portions are thrown farther from the disk, and the heavier portions nearer to the same, the material is automatically assorted as to size and weight. As the disk revolves these assorted portions fall through properly graded apertures into separate channels of a circular trough, from whence they are swept out by brushes secured to a support revolving with the disk.
