ON METALS.PART 1.
George and Harry, with their tutor, one day in their walk, were driven by the rain to take shelter in a blacksmith’s shop; and the shower lasting some time, the boys, in order to amuse themselves, began to examine the things around them. The great bellows first attracted their notice, and they admired the roaring it made, and the expedition with which it raised the fire to a heat too intense for them to look at. They were surprised at the dexterity with which the smith fashioned a bar of iron into a horseshoe;first heatingit, then hammering it well on the anvil, cutting off a proper length, bending it round, turning up the ends, and lastly, punching the nail-holes. They watched the whole process of fitting it to the horse’s foot, and fastening it on; and it had become fair some minutes before they showed a desire to leave the shop and proceed on their walk.
“I should never have thought,” says George, beginning the conversation, “that such a hard thing as iron could have been so easily managed.”
“Nor I neither,” said Harry.
Tut.It was managed, you saw, by the help of fire. The fire made it soft and flexible, so that the smith could easily hammer it, and cut it, and bend it to the shape he wanted; and then dipping it in the water made it hard again.
Geo.Are all other metals managed in the same manner?
Tut.They are all worked by the help of fire in some way or other, either in melting them, or making them soft.
Geo.There are a good many sorts of metals, are there not?
Tut.Yes, several; and if you have a mind I will tell you about them, and their uses.
Geo.Pray do, sir.
Har.Yes; I should like to hear it of all things.
Tut.Well, then. First, let us consider what a metal is. Do you think you should know one from a stone?
Geo.A stone!—Yes, I could not mistake a piece of lead or iron for a stone.
Tut.How would you distinguish it?
Geo.A metal is bright and shining.
Tut.True—brilliance is one of their qualities. But glass and crystal are very bright, too.
Har.But one may see through glass, and not through a piece of metal.
Tut.Right. Metals are brilliant, but opaque, or not transparent. The thinnest plate of metal that can be made will keep out the light as effectually as a stone-wall.
Geo.Metals are very heavy, too.
Tut.True. They are the heaviest bodies in nature; for the lightest metal is nearly twice as heavy as the heaviest stone. Well, what else?
Geo.Why, they will bear beating with a hammer, which a stone would not, without flying in pieces.
Tut.Yes: that property of extending or spreading under the hammer,is calledmalleability; and another, like it, is that of bearing to be drawn out into a wire, which is calledductility. Metals have both these, and much of their use depends upon them.
Geo.Metals will melt, too.
Har.What! will iron melt?
Tut.Yes; all metals will melt, though some require greater heat than others. The property of melting is calledfusibility. Do you know anything more about them?
Geo.No; except that they come out of the ground, I believe.
Tut.That is properly added, for it is this circumstance which makes them rank amongfossils, or minerals. To sum up their character, then, a metal is a brilliant, opaque, heavy, malleable, ductile, and fusible mineral.
Geo.I think I can hardly remember all that.
Tut.Thenamesmay slip your memory, but you cannot see metals at all used, without being sensible of thethings.
Geo.But what areores? I remember seeing a heap of iron ore which men were breaking with hammers, and it looked only like stones.
Tut.Theoreof a metal is the state in which it is generally met with in the earth, when it is so mixed with stony and other matters, as not to show its proper qualities as a metal.
Har.How do people know it, then?
Tut.By experience. It was probably accident that in the early ages discovered that certain fossils by the force of fire might be made to yield a metal. The experiment was repeated on other fossils; so that in length of time all the different metals were found out, and all the different forms in which they lie concealed in the ground. The knowledge of this is calledmineralogy, and a very important science it is.
Geo.Yes, I suppose so: for metals are very valuable things. Our next neighbour, Mr. Stirling, I have heard, gets a great deal of money every year, from his mines in Wales.
Tut.He does. The mineral riches of some countries are much superior to that of their products above ground, and the revenues of many kings are in great part derived from their mines.
Har.I suppose they must be gold and silver mines?
Tat.Those, to be sure, are the most valuable, if the metals are found in tolerable abundance. But do you know why they are so?
Har.Because money is made of gold and silver.
Tut.That is a principal reason, no doubt. But these metals haveintrinsic properties that make them highly valuable, else probably they would not have been chosen in so many countries to make money of. In the first place, gold and silver are bothperfect metals, that is, indestructible in the fire. Other metals, if kept a considerable time in the fire, change by degrees into an earthy, scaly matter, called an oxide. You have melted lead, I dare say?
Geo.Yes, often.
Tut.Have you not, then, perceived a drossy film collect upon its surface, after it had kept melting a while?
Geo.Yes.
Tut.That is an oxide; and in time the whole lead would change to such a substance. You may see, too, when you have heated the poker red-hot, some scales separate from it, which are brittle.
Har.Yes, the kitchen poker is almost burnt away by putting into the fire.
Tut.Well—all metals undergo these changes, except gold and silver; but these, if kept ever so long in the hottest fire, sustain no loss or change. They are therefore calledperfect metals. Gold has several other remarkable properties. It is the heaviest of all metals.
Har.What, is it heavier than lead?
Tut.Yes—about half as heavy again. It is between nineteen and twenty times as heavy as an equal bulk of water. This great weight is a ready means of discovering counterfeit gold coin from genuine; for as gold must be adulterated with something much lighter than itself, a false coin, if of the same weight with the true, will be sensibly bigger. Gold, too, is the most ductile of all metals. You have seen gold-leaf?
Geo.Yes; I bought a book of it once.
Tut.Gold-leaf is made by beating a plate of gold placed between pieces of skin, with heavy hammers, till it is spread out to the utmost degree of thinness. And so great is its capacity for being extended, that a single grain of the metal, which would be scarce bigger than a large pin’s head, is beaten out to a surface of fifty square inches.
Geo.That is wonderful, indeed! But I know gold-leaf must be very thin, for it will almost float upon the air.
Tut.By drawing gold out to a wire, it may be still farther extended. Gold wire, as it is called, is made with silver overlaid with a small proportion of gold, and they are drawn out together. In the wire commonly used for laces, and embroidery, and the like, a grain of gold is made completely to cover a length of three hundred and fifty-two feet; andwhen it is stretched still farther by flatting, it will reach four hundred and one feet.
Geo.Prodigious! What a vast way a guinea might be drawn out, then!
Tut.Yes, the gold of a guinea at that rate would reach above nine miles and a half. This property in gold of being capable of extension to so extraordinary a degree, is owing to its great tenacity or cohesion of particles, which is such, that you can scarcely break a piece of gold wire by twisting it.
Har.Then it would make very good wire for hanging bells.
Tut.It would; but such bell-hanging would come rather too dear. Another valuable quality of gold, is its fine colour. You know scarce anything makes a more splendid appearance than gilding. And a peculiar advantage of it is, that gold is not liable to rust or tarnish, as other metals are. It will keep its colour fresh for a great many years, in a pure and clear air.
Har.I remember the vane of the church-steeple was new-gilt two years ago, and it looks as well as at first.
Tut.This property of not rusting would render gold very useful for a variety of purposes, if it were more common. It would make excellent cooking utensils, water-pipes, mathematical instruments, clockwork, and the like.
Geo.But is not gold soft? I have seen pieces of gold bent double.
Tut.Yes; it is next in softness to lead, and, therefore, when it is made into coin, or used for any common purposes, it is mixed with a small proportion of some other metal, in order to harden it. This is called itsalloy. Our gold coin has one twelfth of alloy, which is copper.
Geo.How beautiful new gold coin is!
Tut.Yes—scarce any metal takes a stamp or impression better; and it is capable of a very fine polish.
Geo.What countries yield the most gold?
Tut.South America, the East Indies, and the coast of Africa. Europe affords but little; yet a moderate quantity is got every year from Hungary.
Geo.I have heard of rivers rolling sands of gold. Is there any truth in that?
Tut.The poets, as usual, have exaggerated the matter: however, there are various streams in different parts of the world, the sands of which contain particles of gold, and some of them in such quantity as to be worth the search.
Har.How does the gold come there?
Tut.It is washed down along with the soil from mountains by the torrents which are the sources of rivers. Some persons say that all sands contain gold; but I would not advise you to take the pains to search for it in our common sand: for, in more senses than one,gold may be bought too dear.
Har.But what a fine thing it would be to find a gold mine on one’s estate!
Tut.Perhaps not so fine as you may imagine, for many a one does not pay the cost of working. A coal-pit would probably be a better thing. Who do you think are the greatest gold-finders in Europe?
Har.I don’t know.
Tut.The gipsies in Hungary. A number of half-starved, half-naked wretches of that community employ themselves in washing and picking the sands of some mountain-streams in that country which contain gold, from which they obtain just profit enough to keep body and soul together: whereas, did they employ themselves in agriculture or manufactures, they might have got a comfortable subsistence. Gold, almost all the world over, is first got by slaves, and it makes slaves of those who possess much of it.
Geo.For my part, I will be content with a silver mine.
Har.But we have none of those in England, have we?
Tut.We have no silver mines, properly so called, but silver is procured in some of our lead mines. There are, however, valuable silver mines in various parts of Europe; but the richest of all are in Peru, in South America.
Geo.Are not the famous mines of Potosi there?
Tut.They are. Shall I now tell you some of the properties of silver?
Geo.By all means.
Tut.It is anotherperfectmetal. It is also as little liable to rust as gold, though indeed it readily gets tarnished.
Har.Yes; I know our footman is often obliged to clean our plate before it is used.
Tut.Plate, however, is not made of pure silver, any more than silver coin, and silver utensils of all kinds. Copper is mixed with it, as with gold, to harden it; and that makes it more liable to tarnish.
Geo.Bright silver, I think, is almost as beautiful as gold.
Tut.It is the most beautiful of the white metals, and is capable of avery fine polish; and this, together with its rarity, makes it used for a great variety of ornamental purposes. Then it is nearly as ductile and malleable as gold.
Geo.I have had silver-leaf, and it seemed as thin as gold-leaf.
Tut.It is nearly so. That is used for silvering, as gold-leaf is for gilding. It is common, too, to cover metals with a thin coating of silver which is called plating.
Har.The child’s saucepan is silvered over on the inside. What is that for?
Tut.To prevent the victuals from getting any taint from the metal of the saucepan; for silver is not capable of being corroded or dissolved by any of the liquids used for food, as iron and copper are.
Har.And that is the reason I suppose that fruit-knives are made of silver.
Tut.It is; but the softness of the metal makes them bear a very poor edge.
Geo.Does silver melt easily?
Tut.Silver and gold both melt more difficultly than lead; not till they are above a common red heat. As to the weight of silver, it is nearly one half less than that of gold, being only eleven times as heavy as water.
Har.Is quicksilver a kind of silver?
Tut.It takes its name from silver, being very like it in colour; but in reality it is a very different thing, and one of the most singular of the metal kind.
Geo.It is notmalleable, I am sure.
Tut.No; not when it is quick or fluid, as it always is in our climate. But a very great degree of cold makes it solid, and then it is malleable like other metals.
Geo.I have heard ofkillingquicksilver; pray, what does that mean?
Tut.It means destroying its property of running about, by mixing it with something else. Thus if quicksilver be well rubbed with fat, or oil, or gum, it unites with them, losing all its metallic appearance or fluidity. It also unites readily with gold and silver, and several other metals, into a kind of shining paste, which is called anamalgam. This is one of the ways of gilding or silvering a thing. Your buttons are gilt by means of an amalgam.
Geo.How is that done?
Tut.The shells of the buttons, which are made of copper, are shakenin a hat with a lump of amalgam of gold and quicksilver, till they are all covered over with it. They are then put into a sort of frying-pan, and held over the fire. The quicksilver, being very volatile in its nature, flies off in the form of a smoke or vapour when it is heated, leaving the gold behind it spread over the surface of the button. Thus many dozens are gilt at once with the greatest ease.
Geo.What a clever way! I should like vastly to see it done.
Tut.You may see it any day at Birmingham, if you happen to be there; as well as a great many other curious operations on metals.
Geo.What a weight quicksilver is! I remember taking up a bottleful of it, and I had liked to have dropped it again, it was so much heavier than I expected.
Tut.Yes, it is one of the heaviest of the metals—about fifteen times as heavy as water.
Geo.Is notmercurya name for quicksilver? I have heard them talk of the mercury rising and falling in the weather-glass.
Tut.It is. You, perhaps, may have heard too ofmercurial medicines, which are those made of quicksilver prepared in one manner or another.
Geo.What are they good for?
Tut.For a great variety of complaints. Your brother took some lately for the worms; and they are often given for breakings-out on the skin, and for sores and swellings. But they have one remarkable effect, when taken in a considerable quantity, which is to loosen the teeth, and cause a great spitting. This is called salivation.
Har.I used to think quicksilver was poison.
Tut.When it is in its common state of running quicksilver it generally does neither good nor harm; but it may be prepared, so as to be a very violent medicine, or even a poison.
Geo.Is it useful for anything else?
Tut.Yes—For a variety of purposes in the arts, which I cannot now very well explain to you. But you will perhaps be surprised to hear that one of the finest red paints is made from quicksilver.
Geo.A red paint!—which is that?
Tut.Vermilion, or cinnabar, which is a particular mixture of sulphur with quicksilver.
Har.Is quicksilver found in this country?
Tut.No. The greatest quantity comes from Spain, Istria, and South America. It is a considerable object of commerce, and bears a high value,though much inferior to silver. Well, so much for metals at present. We will talk of the rest on some future opportunity.