ON METALS.PART II.
Tutor—George—Harry.
Tutor—George—Harry.
Tutor—George—Harry.
Tutor.Well—have you forgotten what I told you about metals the other day?
George.O no!
Harry.I am sure I have not.
Tut.What metals were they that we talked about?
Geo.Gold, silver, and quicksilver.
Tut.Suppose, then, we go on to the rest?
Geo.Pray, do.
Har.Yes, by all means.
Tut.Very well. You knowcopper, I don’t doubt?
Geo.O yes!
Tut.What colour do you call it?
Geo.I think it is a sort of reddish brown.
Tut.True. Sometimes, however, it is of a bright red, like sealing-wax. It is not a very heavy metal, being not quite nine times the weight of water. It is very ductile, bearing to be rolled or hammered out to a very thin plate, and also to be drawn out to a fine wire.
Har.I remember seeing a penny that had been rolled out to a long riband.
Geo.Yes, and I have seen half a dozen men at a time with great hammers beating out a piece of copper at the brazier’s.
Tut.Copper requires a very considerable heat to melt it: and by long exposure to the fire, it may be burnt or calcined; for, like all we are now to speak of, it is animperfectmetal.
Har.And it rusts very easily, does it not?
Tut.It does; for all acids dissolve or corrode it, so do salts of every kind: whence even air and common water in a short time act upon it, for they are never free from somewhat of a saline nature.
Geo.Is not verdigris the rust of copper?
Tut.It is; a rust produced by the acid of grapes. But every rust of copper is of a blue or green colour, as well as verdigris.
Har.And are they all poison, too?
Tut.They are all so in some degree, producing violent sickness and pain in the bowels. They are all, too, extremely nauseous to the taste, and the metal itself when heated, tastes and smells very disagreeably.
Har.Why is it used, then, so much in cooking, brewing, and the like?
Tut.Because it is a very convenient metal for making vessels, especially large ones, as it is easily worked, and is sufficiently strong, though hammered thin, and bears the fire well. And if vessels of it are kept quite clean, and the liquor not suffered to stand long in them when cold there is no danger in their use. But copper vessels for cooking are generally lined on the inside with tin.
Geo.What else is copper used for?
Tut.A variety of things. Sheets of copper are sometimes used to cover buildings; and of late a great quantity is consumed in sheathingships, that is, in covering all the part under water; the purpose of which is, to protect the timber from the worms, and also to make the ship sail faster, by means of the smoothness and therefore less obstruction which the copper offers to the water, as the ship is forced through it by the action of the wind on the sails.
Har.Money is made of copper, too.
Tut.It is; for it takes an impression in coining very well, and its value is a proper proportion below silver, for a price for the cheapest commodities. In some poor countries they have little other than copper coin. Another great use of copper is as an ingredient in mixed metals, such as bell-metal, cannon-metal, and particularly brass.
Har.But brass is yellow.
Tut.True; it is converted to that colour by means of another metallic substance, namedzincorspelter, the natural colour of which is white. A kind of brown stone calledcalamineis an ore of zinc. By filling a pot with layers of powdered calamine and charcoal placed alternately with copper, and applying a pretty strong heat, the zinc is driven in vapour out of the calamine, and penetrates the copper, changing it into brass.
Geo.What is the use of turning copper into brass?
Tut.It gains a fine gold-like colour, and becomes harder, more easy to melt, and less liable to rust. Hence it is preferred for a variety of utensils, ornamental and useful. Brass does not bear hammering well, but is generally cast into the shape wanted, and then turned in a lathe and polished. Well—these are the principal things I have to say about copper.
Har.But where does it come from?
Tut.Copper is found in many countries. The Isle of Great Britain yields abundance, especially in Wales and Cornwall. In Anglesey is a whole hill called Paris Mountain, consisting of copper-ore, from which immense quantities are dug every year. Now foriron.
Har.Ay! that is the most useful of all the metals.
Tut.I think it is; and it is likewise the most common, for there are few countries in the world possessing hills and rocks, where it is not met with, more or less. Iron is the hardest of metals, the most elastic or springy, very tenacious or difficult to break, the most difficultly fusible, and one of the lightest, being only seven or eight times as heavy as water.
Geo.You say it is difficult to break; but I snapped the blade of a penknife the other day by only bending it a little; and my mother is continually breaking her needles.
Tut.Properly objected; but the qualities of iron differ extremely according to the method of preparing it. There are forged iron, cast iron, and steel, which are very different from each other. Iron, when first melted from its ore, has little malleability, and the vessels and other implements that are made of it in that state, by casting into moulds, are easily broken. It acquires toughness and malleability byforging, which is done by beating it when red-hot with heavy hammers, till it becomes ductile and flexible. Steel, again, is made byheating small bars of iron with charcoal, bone, and horn shavings, or other inflammable matters, by which it acquires a finer grain and more compact texture, and becomes harder, and more elastic. Steel may be rendered either very flexible or brittle, by different manners oftempering, which is performed by heating and then quenching it in water.
Geo.All cutting instruments are made of steel, are they not?
Tut.Yes; and the very fine-edged ones are generally tempered brittle, as razors, penknives, and surgeons’ instruments; but sword-blades are made flexible, and the best of them will bend double without breaking or becoming crooked. The steel of which springs are made has the highest possible degree of elasticity given it. A watch-spring is one of the most perfect examples of this kind. Steel for ornaments is made extremely hard and close-grained, so as to bear an exquisite polish. Common hammered iron is chiefly used for works of strength, as horseshoes, bars, bolts, and the like. It will bend but not straighten itself again, as you may see in the kitchen poker. Cast iron is used for pots and caldrons, cannons, cannon-balls, grates, pillars, and many other purposes in which hardness without flexibility is wanted.
Geo.What a vast variety of uses this metal is put to!
Tut.Yes; I know not when I should have done, if I were tell you of all.
Har.Then I think it is really more valuable than gold, though it is so much cheaper.
Tut.That was the opinion of the wise Solon, when he observed to the rich king Crœsus, who was showing him his treasures, “He who possesses more iron will soon be master of all this gold.”
Har.I suppose he meant weapons and armour?
Tut.He did; but there are many nobler uses for these metals; and few circumstances denote the progress of the arts in a country more than having attained the full use of iron, without which scarcely any manufacture or machinery can be brought to perfection. From the difficulty ofmelting it out of the ore, many nations have been longer in discovering it than some of the other metals. The Greeks, in Homer’s time, seem to have employed copper or brass for their weapons much more than iron; and the Mexicans and Peruvians, who possessed gold and silver, were unacquainted with iron, when the Spaniards invaded them.
Geo.Iron is very subject to rust, however.
Tut.It is so, and that is one of its worst properties. Every liquor, and even a moist air corrode it. But the rust of iron is not pernicious: on the contrary, it is a very useful medicine.
Geo.I have heard of steel drops and steel filings given for medicine.
Tut.Yes; iron is given in a variety of forms, and the property of them all is to strengthen the constitution. Many springs are made medicinal by the iron that they dissolve in the bowels of the earth. These are calledchalybeatewaters, and they may be known by their inky taste, and the rust-coloured sediment they leave in their course.
Har.May we drink such water if we meet with it?
Tut.Yes; it will do you no harm, at least. There is one other property of iron, well worth knowing, and that is, that it is the only thing attracted by the magnet or loadstone.
Geo.I had a magnet once that would take up needles and keys; but it seemed a bar of iron itself.
Tut.True. The real loadstone, which is a particular ore of iron, can communicate its virtue to a piece of iron by rubbing it; nay, a bar of iron itself, in length of time, by being placed in a particular position, will acquire the same property.
Geo.Is all the iron used in England produced there?
Tut.By no means. Their extensive manufactures require a great importation of iron. Much is brought from Norway, Russia, and Sweden; and the Swedish is reckoned particularly excellent. Well, now to another metal. I dare say you can tell me a good deal aboutlead?
Har.I know several things about it. It is very heavy and soft, and easily melted.
Tut.True; these are some of its distinguishing properties. Its weight is between eleven and twelve times that of water. Its colour is a dull bluish white; and from this livid hue, as well as its being totally void of spring or elasticity, it has acquired a sort of character, of dulness and sluggishness. Thus we say of a stupid man, that he has aleadendisposition.
Geo.Lead is very malleable, I think?
Tut.Yes; it may be beaten out into a pretty thin leaf, but it will not bear drawing into fine wire. It is not only very fusible, but very readily oxidized by heat, changing into a powder, or a scaly matter, which may be made to take all colours by the fire, from yellow to deep red. You have seen red lead?
Geo.Yes.
Tut.That is oxide of lead exposed for a considerable time to a strong flame. Lead may even be changed into glass by a moderate heat; and there is a good deal of it in our finest glass.
Geo.What is white lead?
Tut.It is lead corroded by the steam of vinegar. Lead in various forms is much used by painters. Its oxides dissolve in oil, and are employed for the purpose of thickening paint and making it dry. All lead paints, however, are unwholesome as long as they continue to smell, and the fumes of lead, when melted, are likewise pernicious. This is the cause why painters and plumbers are so subject to various diseases, particularly violent colics and palsies. The white-lead manufacture is so hurtful to the health, that the workmen, in a very short time, are apt to lose the use of their limbs, and be otherwise severely indisposed.
Geo.I wonder, then, that anybody will work in it.
Tut.Ignorance and high wages are sufficient to induce them. But it is to be lamented that in a great many manufactures the health and lives of individuals are sacrificed to the convenience and profit of the community. Lead, too, when dissolved, as it may be in all sour liquors, is a slow poison, and the more dangerous, as it gives no disagreeable taste. A salt of lead made with vinegar, is so sweet, as to be called the sugar of lead. It has been too common to put this or some other preparation of lead into sour wines, in order to cure them; and much mischief has been done by this practice.
Geo.If lead is poisonous, is it not wrong to make water-pipes and cisterns of it?
Tut.This has been objected to; but it does not appear that water can dissolve any of the lead. Nor does it readily rust in the air, and hence it is much used to cover buildings with, as well as to line spouts and water-courses. For these purposes the lead is cast into sheets, which are easily cut and hammered into any shape.
Har.Bullets and shot, too, are made of lead.
Tut.They are; and in this way they are ten times more destructive than as a poison.
Geo.I think lead seems to be more used than any metal except iron.
Tut.It is; and the plenty of it in our country is a great benefit to us, both for domestic use, and as an article that brings in much profit by exportation.
Geo.Where are our principal lead mines?
Tut.They are much scattered about. The west of England produces some, in Cornwall, Devonshire, and Somersetshire. Wales affords a large quantity. Derbyshire has long been noted for its lead mines, and so have Northumberland and Durham. And there are considerable ones in the southern part of Scotland. Now do you recollect another metal to be spoken about?
Geo.Tin.
Tut.True. Tin resembles lead in colour, but has a more silvery whiteness. It is soft and flexible, like lead, but is distinguished by the crackling noise it makes on being bent. It melts as easily as lead, and also is readily oxidized by keeping it in the fire. It is the lightest of the metals, being only seven times as heavy as water. It may be beaten into a thin leaf, but not drawn out to wire.
Geo.Is tin of much use?
Tut.It is not often used by itself, but very frequently in conjunction with other metals. As tin is little liable to rust, or to be corroded by common liquors, it is employed for a lining or coating of vessels made of copper or iron. The saucepans and kettles in the kitchen, you know, are all tinned.
Geo.Yes; how is it done?
Tut.By melting the tin, and spreading it upon the surface of the copper, which is first heated, in order to make the tin adhere.
Geo.But what are the vessels made at the tinman’s? Are they not all tin?
Tut.No.Tinnedware, as it is properly called, is made of thin iron plates, coated over with tin by dipping them into a vessel full of melted tin. These plates are afterward cut and bent to proper shapes, and the joinings are soldered together with a mixture of tin and other metals. Another similar use of tin is in what is called the silvering of pins.
Geo.What—is not that real silvering?
Tut.No. The pins which are made of brass wire, after being pointedand headed, are boiled in hot water, in which grain-tin is put along with tartar, which is a crust that collects on the inside of wine casks. The tartar dissolves some of the tin, and makes it adhere to the surface of the pins, and thus thousands are covered in an instant.
Har.That is as clever as what you told us of the gilding of buttons!
Tut.It is. Another purpose for which great quantities of tin used to be employed was the making of pewter. The best pewter consists chiefly of tin, with a small mixture of other metals to harden it; and the London pewter was brought to such perfection as to look almost as well as silver.
Geo.I can just remember a long row of pewter plates at my grandmother’s.
Tut.You may. In her time all the plates and dishes for the table were made of pewter, and a handsome range of pewter shelves was thought a capital ornament for a kitchen. At present, this trade is almost come to nothing, through the use of earthenware and china; and pewter is employed for little but the worms of stills, and barbers’ basins, and porter-pots. But a good deal is still exported. Tin is likewise an ingredient in other mixed metals for various purposes, but, on the whole, less of it is used than of the other common metals.
Geo.Is not England more famous for tin than any other country? Ihave read of the Phoenicians trading here for it in very early times.
Tut.They did; and tin is still a very valuable article of export from England. Much of it is sent as far as China. The tin mines are chiefly in Cornwall, England, and I believe they are the most productive of any in Europe. Very fine tin is also got in the peninsula of Malacca in the East Indies. Well—we have now gone through the metals.
Geo.But you said nothing about a kind of metal called zinc.
Tut.That is one of another class of mineral substances calledsemi-metals. These resemble metals in every quality but ductility, of which they are almost wholly destitute, and for want of it they can seldom be used in the arts, except when joined with metals.
Geo.Are there many of them?
Tut.Yes, several; but we will not talk of them till I have taken some opportunity of showing them to you, for probably you may never have seen any of them. Now try to repeat the names of all the metals to me in the order of their weight.
Har.There is firstgold.
Geo.Thenquicksilver,lead,silver.
Har.Copper,iron,tin.
Tut.Very right. Now I must tell you of an old fancy that chymists have had of christening these metals by the names of the heavenly bodies. They have called goldSol, or the sun.
Geo.That is suitable enough to its colour and brightness.
Har.Then silver should be the moon, for I have heard moonlight called of a silvery hue.
Tut.True; and they have named it so. It isLuna. Quicksilver isMercury, so named probably from its great propensity to dance and jump about, forMercury, you know, was very nimble.
Geo.Yes—he had wings to his heels.
Tut.Copper isVenus.
Geo.Venus!surely it is scarcely beautiful enough for that.
Tut.But they had disposed of the most beautiful ones before. Iron is Mars.
Har.That is right enough, because swords are made of iron.
Tut.True. Then tin isJupiter, and leadSaturn. I suppose only to make out the number. Yet the dulness of lead might be thought to agree with that planet which is most remote from the sun. These names, childish as they may seem, are worth remembering, since chymists and physicians still apply them to many preparations of the various metals. You will, probably, often hear ofmartial,lunar,mercurial, andsaturnine; and you may now know what they mean.
Geo.I think the knowledge of metals seems more useful than all you have told us about plants.
Tut.I don’t know that. Many nations make no use at all of metals, but there are none which do not owe a great part of their subsistence to vegetables. However, without inquiring what parts of natural knowledge aremostuseful, you may be assured of this, that all are useful in some degree or other; and there are few things that give one man greater superiority over another, than the extent and accuracy of his knowledge in these particulars. One person passes all his life upon the earth, a stranger to it; while another finds himself at home everywhere.