Popular Technology Volume II Part 20

10. Although these useful implements are made in London, and in several other places in England, yet Gloucester is the princ.i.p.al seat of this manufacture in that kingdom. It was introduced into that place, in 1626, by John Silsby, and it now contains nine distinct manufactories, in which are employed about 1500 persons, chiefly women and children. Pins are also manufactured extensively in the villages near Paris, and in several other places in France, as well as in Germany.

11. The business of making pins has been lately commenced in the city of New-York, and it is said that the experiment has been so successful, both in the perfection of the workmanship, and in the rapidity of the production, that pins of American manufacture bid fair to compete, at least, with those of foreign countries.

[Ill.u.s.tration: TINPLATE WORKER.]

THE TINPLATE WORKER, &c.

TIN.

1. Tin is a whitish metal, less elastic, and less sonorous than any other metal, except lead. It is found in the mountains which separate Gallicia from Portugal, and in the mountains between Saxony and Bohemia. It also occurs in the peninsula of Molucca, in India, Mexico, and Chili. But the mines of Cornwall and Devonshire, in England, are more productive than those of all other countries united.

2. There are two ores of tin, one of which is called _tin stone_, and the other _tin pyrites_; the former of these is the kind from which the metal is extracted. The ore is usually found in veins, which often penetrate the hardest rocks. When near the surface of the earth, or at their commencement, they are very small, but they increase in size, as they penetrate the earth. The direction of these veins, or, as the miners call them, _lodes_, is usually east and west.

3. The miners follow the lode, wheresoever it may lead; and, when they extend to such a depth, that the waters become troublesome in the mine, as is frequently the case, they are pumped up with machinery worked by steam, or drawn off by means of a drain, called an _adit_.

The latter method is generally adopted, when practicable.

4. The ore is raised to the surface through shafts, which have been sunk in a perpendicular direction upon the vein. At the top of the shaft, is placed a windla.s.s, to draw up the _kibbuts_, or baskets, containing the ore. Near St. Austle, in Cornwall, is a mine which has not less than fifty shafts, half of which are now in use. Some of the veins have been worked a full mile, and some of the shafts are nearly seven hundred feet deep.

5. At St. Austle Moor, there is a mine of _stream tin_, about three miles in length. The tin, together with other substances, has been deposited in a valley, by means of small streams from the hills. The deposite is about twenty feet deep, and the several materials of which it is composed, have settled in strata, according to their specific gravity. The ore, being the heaviest, is, of course, found at the bottom.

6. The ore, from whatever source it may be obtained, is first pulverized in a stamping mill, and then washed, to free it from the stony matter with which it may be united. The ore, thus partially freed from foreign matter, is put into a reverberatory furnace, with fuel and limestone, and heated intensely. The contents of the furnace having been brought to a state of fusion, the lime unites with the earthy matters, and flows with them into a liquid gla.s.s, while the carbon of the coal unites with the tin. The metal sinks, by its specific gravity, to the bottom of the furnace, and is let out, after having been exposed to the heat about ten hours.

7. The tin thus obtained, is very impure; it therefore requires a second fusion, to render it fit for use. After having been melted a second time, it is cast into blocks weighing about three hundred pounds. These blocks are taken to places designated by law, and there stamped, by inspectors appointed for the purpose by the Duke of Cornwall. In performing this operation, the inspector cuts off a corner, and stamps the block at that place, with the proper seal, and with the name of the smelter. These precautions give a.s.surance, that the metal is pure, and that the duty has been paid.

8. The duty is four shillings sterling per hundred weight, which is paid to the Duke of Cornwall, who is also Prince of Wales. The revenue from this source amounts to about thirty thousand pounds a year. The owner of the soil also receives one sixth, or one eighth of the ore as his _dish_, as the miners call it. The miners and the smelters receive certain proportions of the metal for their services.

9. Tin was procured from Britain at a very early period. The Phoenicians are said by Strabo to have pa.s.sed the Pillars of Hercules, now the Straits of Gibraltar, about 1200 years before Christ. But the time at which they discovered the tin islands, which they denominated _Ca.s.sorides_, cannot be ascertained from history, although it is evident from many circ.u.mstances, that the Scilly Islands, and the western ports of Britain, were the places from which these early navigators procured the tin with which they supplied the parts of the world to which they traded.

10. For a long time, the Phoenicians and the Carthaginians enjoyed the tin trade, to the exclusion of all other nations. After the destruction of Carthage by the Romans, a colony of Phocean Greeks, established at Ma.r.s.eilles, carried on this trade; but it came into the hands of the Romans, after the conquest of Britain by Julius Caesar.

11. The Cornish mines furnish incontestable proofs of having been worked many hundred years ago. In digging to the depth of forty or fifty fathoms, the miners frequently meet with large timbers imbedded in the ore. Tools for mining have also been found in the same, or similar situations. The mines, therefore, which had been exhausted of the ore, have, in the course of time, been replenished by a process of nature.

12. To what purposes the ancients applied all the tin which they procured at so much labor and cost, is not precisely known. It is probable, that the Tyrians consumed a portion of it, in dyeing their purple and scarlet. It formed then, as it now does, many important alloys with copper. The mirrors of antiquity were made of a composition of these metals.

13. The method of extracting tin from its ores was probably very defective in ancient times. At least, it was so for several centuries before the time of Elizabeth, when Sir Francis G.o.dolphin introduced great improvements in the tin works. The use of the reverberatory furnace was commenced, about the beginning of the eighteenth century, and soon after pit-coal was subst.i.tuted for charcoal.

14. This metal, in its solid state, is called _block-tin_. It is applied, without any admixture with any other metal, to the formation of vessels, which are not to be exposed to a temperature much above that of hot water. A kind of ware, called _biddery ware_, is made of tin alloyed with a little copper. The vessels made of this composition, are rendered black by the application of nitre, common salt, and sal ammoniac. _Foil_ is also made by pressing it between steel rollers, or by hammering it, as in the case of gold by the gold-beaters.

15. But tin is most extensively applied as a coating to other metals, stronger than itself, and more subject to oxydation. The places which are usually denominated tin, are thin sheets of iron coated with this metal. The iron is reduced to thin plates in a rolling-mill, and these are prepared for being tinned, by first steeping them in water acidulated with muriatic acid, and then freeing them from oxyde by heating, scaling, and rolling them.

16. The tin is melted in deep oblong vessels, and kept in a state of fusion by a charcoal fire. To preserve its surface from oxydation, a quant.i.ty of fat or oil is kept floating upon it. The plates are dipped perpendicularly into the tin, and held there for some time. When withdrawn, they are found to have acquired a bright coating of the melted metal. The dipping is performed three times for _single tin plate_, and six times for _double tin plate_. The tin penetrates the iron, and forms an alloy.

17. Various articles of iron, such as spoons, nails, bridle-bits, and small chains, are coated with tin, by immersing them in that metal, while in a state of fusion. The great affinity of tin and copper, renders it practicable to apply a thin layer of the former metal to the surface of the latter; and this is often done, as stated in the article on the coppersmith.

18. Tin and quicksilver are applied to the polished surface of gla.s.s, for the purpose of forming mirrors. In silvering plain looking-gla.s.ses, a flat, horizontal slab is used as a table. This is first covered with paper, and then with a sheet of tin foil of the size of the gla.s.s. A quant.i.ty of quicksilver is next laid on the foil, and spread over it with a roll of cloth, or with a hare's foot.

19. After as much quicksilver as the surface will hold, has been spread on, and while it is yet in a fluid state, the gla.s.s is shoved on the sheet of foil from the edge of the table, driving a part of the liquid metal before it. The gla.s.s is then placed in an inclined position, that every unnecessary portion of the quicksilver may be drained off, after which it is again laid flat upon the slab, and pressed for a considerable time with heavy weights. The remaining quicksilver amalgamates with the tin, and forms a permanent, reflecting surface.

THE TIN-PLATE WORKER.

1. The materials on which the tinner, or tin-plate worker, operates, are the rolled sheets of iron, coated with tin, as just described. He procures the sheets by the box, and applies them to the roofs and other parts of houses, or works them up into various utensils, such as pails, pans, bake-ovens, measures, cups, and ducts for conveying water from the roofs of houses.

2. In making the different articles, the sheets are cut into pieces of proper size, with a huge pair of shears, and these are brought to the proposed form by different tools, adapted to the purpose. The several parts are united by means of a solder made of a composition of tin and lead. The solder is melted, and made to run to any part, at the will of the workman, by means of a copper instrument, heated for the purpose in a small furnace with a charcoal fire.

3. On examining almost any vessel of tin ware, it will be perceived, that, where the parts are united, one of the edges, at least, and sometimes both, are turned, that the solder may be easily and advantageously applied. It will also be discovered that iron wire is applied to those parts requiring more strength than is possessed by the tin itself. The edges and handles are especially strengthened in this manner.

4. The edges of the tin were formerly turned on a steel edge, or a kind of anvil called a _stock_, with a mallet; and, in some cases, this method is still pursued; but this part of the work is now more expeditiously performed, by means of several machines invented by Seth Peck, of Hartford Co., Connecticut. These machines greatly expedite the manufacture of tin wares, and have contributed much towards reducing their price.

5. This manufacture is an extensive branch of our domestic industry; and vast quant.i.ties of tin, in the shape of various utensils, are sold in different parts of the United States, by a cla.s.s of itinerant merchants, called _tin-pedlers_, who receive in payment for their goods, rags, old pewter, bra.s.s, and copper, together with feathers, hogs' bristles, and sometimes ready money.

LEAD.

1. Next to iron, lead is the most extensively diffused, and the most abundant metal. It is found in various combinations in nature; but that mineralized by sulphur is the most abundant. This ore is denominated _galena_ by the mineralogists, and is the kind from which nearly all the lead of commerce is extracted.

2. The ore having been powdered, and freed, as far as possible, from stony matter, is fused either in a blast or reverberatory furnace. In the smelting, lime is used as a flux, and this combines with the sulphur and earthy matters, while the lead unites with the carbon of the fuel, and sinks to the bottom of the furnace, whence it is occasionally let out into a reservoir.

3. Lead extracted from galena, often contains a sufficient proportion of silver to render it an object to extract it. This is done by oxydizing the lead by means of heat, and a current of air. At the end of this operation, the silver remains with a small quant.i.ty of lead, which is afterwards separated by the process of cupellation. The oxyde is applied to the purposes for which it is used, or it is reduced again to a metallic state.

4. The lead mines on the Mississippi are very productive, and very extensive. The princ.i.p.al mines are in the neighborhood of Galena, in the north-western part of Illinois, and these are the richest on the globe. The lead mines in the vicinity of Potosi, Missouri, are also very productive. About 3,000,000 pounds are annually smelted in the United States.

5. Lead, on account of its easy fusibility and softness, can be readily applied to a variety of purposes. It is cast in moulds, to form weights, bullets, and other small articles. Cisterns are lined, and roofs, &c., are covered with sheet lead; and also in the construction of pumps and aqueducts, leaden pipes are considerably used. The mechanic who applies this metal to these purposes, is called a plumber.

6. Lead is cast into sheets in sand, on large tables having a high ledge on each side. The melted lead is poured out upon the surface from a box, which is made to move on rollers across the table, and is equalized, by pa.s.sing over it a straight piece of wood called a _strike_. The sheets thus formed, are afterwards reduced in thickness, and spread to greater dimensions, by compressing them between steel rollers.

7. Leaden pipes may be made in various ways. They were at first formed of sheet lead, bent round a cylindrical bar, or mandrel, and then soldered; but pipes formed in this manner, were liable to crack and break. The second method consists in casting successive portions of the tube in a cylindrical mould, having in it a core. As soon as the tube gets cold, it is drawn nearly out of the mould, and more lead is poured in, which unites with the tube previously formed. But pipes cast in this way are found to have imperfections, arising from flaws and air bubbles.

8. In the third method, which is the one most commonly practised, a thick tube of lead is cast upon one end of a long polished iron cylinder, or mandrel, of the size of the bore of the intended pipe.

The lead is then reduced, and drawn out in length, either by drawing it on the mandrel through circular holes of different sizes, in a steel plate, or by rolling it between contiguous rollers, which have a semicircular groove cut round the circ.u.mference of each.

9. The fourth method consists in forcing melted lead, by means of a pump, into one end of a mould, while it is discharged in the form of a pipe, at the opposite end. Care is taken so to regulate the temperature, that the lead is chilled just before it leaves the mould.

10. _Shot_ is likewise made of lead. These instruments of death are usually cast in high towers constructed for the purpose. The lead is previously alloyed with a small portion of a.r.s.enic, to increase the cohesion of its particles, and to cause it to a.s.sume more readily the globular form. It is melted at the top of the tower, and poured into a vessel perforated at the bottom with a great number of holes.

11. The lead, after running through these perforations, immediately separates into drops, which cool in falling through the height of the tower. They are received below in a reservoir of water, which breaks the fall. The shot are then proved by rolling them down a board placed in an inclined position. Those which are irregular in shape roll off at the sides, or stop, while the spherical ones continue on to the end.

[Ill.u.s.tration: IRON-FOUNDER.]

THE IRON-FOUNDER, &c.