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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.
G. What is white lead ?
T. It is lead corroded by the steam of vinegar. Lead in various forms is much used by painters. Its calces 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.
G. I wonder, then, that anybody will work in it.
T. 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.
G. If lead is poisonous, is it not wrong to make water-pipes and cisterns of it?
T. 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.
H. Bullets and shot, too, are made of lead.
T. They are; and in this way it is ten times more destructive than as a poison.
G. I think more lead seems to be used than any metal except iron.
T. 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.
G. Where are our principal lead-mines ?
T. They are much scattered about this island. The west of England produces a great deal, 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 mines in the southern part of Scotland. Now do you recollect another metal to be spoken about?
T. 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 calcined 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.
G. Is tin of much use?
T. 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.
G. Yes. How is it done?
T. By melting the tin, and spreading it upon the surface of the copper, which is first lightly pitched over, in order to make the tin adhere.
H. But what are the vessels made at the tinman's? Are they not called tin ?
T. No. Tinned-ware (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.
G. What! is not that real silvering ?
T. No. The pins, which are made of brass wire, after being pointed and headed, are boiled in 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.
H. That is as clever as what you told us of the gilding of buttons.
T. 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.
G. I can just remember a long row of pewter plates at my grandmother's.
T. 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, barbers' basins, and publicans' 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.
G. Is not England more famous for tin than any other country? I have read of the Phænicians trading here for it in very early times.
T. 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 here are chiefly in Cornwall, 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.
G. But you have mentioned a kind of metal called zinc.
T. That is one of another class of mineral substances called semi-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.
G. Are there many of them ?
T. 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.
H. There is first gold.
T. Quite right. Now I must tell you of an odd fancy that chemists have had of naming these metals after the heavenly bodies. They have called gold, Sol or the Sun.
G. That is suitable enough to its colour and brightness.
H. Then silver should be the moon, for I have heard moonlight called of a silvery hue.
7. True-and they have named it so. It is Luna. Quicksilver is Mercury,* so named probably from its great propensity to dance and jump about, for Mercury, you know, was very nimble.
A swift-footed messenger of the heathen gods
G. Yes—he had wings to his heels.
T. But they had disposed of the most beautiful ones before. Iron is Mars.*
H. That is right enough, because ords are made of iron.
T. True. Then tin is Jupiter, and lead Saturn ; t 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
These names, childish as they may seem, are worth remembering, since chemists and physicians still apply them to many preparations of the various metals. You will probably often hear of martial, lunar, mercurial, and saturnine; and you may now know what they mean.
G. I think the knowledge of metals seems more useful than all you have told us about plants.
T. 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 are most useful, 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. — From ‘Evenings at Home.'
EARTH AND STONES.
H. O yes,
Harry. I WONDER what all this heap of stones is for.
George. I can tell you; it is for the lime-kiln; don't you see it just by?
I do. But what is to be done to them there? G. They are to be burned into lime; don't you know that? H. But what is lime, and what are its uses ?
G. I can tell you one; they lay it on the fields for manure. Don't you remember we saw a number of little heaps of it, that we took for sheep at a distance, and wondered they did not move?
* Mars, the god of war.
However, I believe we had better ask our tutor about it. Will you please, sir, to tell us something about lime ? Tutor. Willingly. But suppose,
as we talked about all sorts of metals some time ago, I should now give you a lecture about stones and earths of all kinds, which are equally valuable, and much more common, than metals.
G. Pray do, sir.
T. Well then: in the first place, the ground we tread upon, to as great a depth as it has been dug, consists for the most part of matter of various appearance and hardness, called by the general name of earths. In common language, indeed, only the soft and powdery substances are so named, while the hard and solid are called stone or rock; but chemists use the same term for all; as, in fact, earth is only crumbled stone, and stone only consolidated earth.
II. What!-has the mould of my garden ever been stone ?
T. The black earth or mould which covers the surface wherever plants grow, consists mostly of parts of rotted vegetables, such as stalks, leaves, and roots, mixed with sand or loose clay; but this only reaches a little way; and beneath it you always come to a bed of gravel, or clay, or stone, of some kind. Now these earths and stones are distinguished into several species, but principally into three, the properties of which make them useful to man for very different purposes, and are therefore very well worth knowing. As you began with asking me about lime, I shall first mention that class of earths from which it is obtained. These have derived their name of calcareous from this very circumstance, calx being lime in Latin; and lime is got from them all in the same way, by burning them in a strong fire. There are many kinds of calcareous earths. One of them is marble ; you know what that is ?
G. O yes! Our parlour chimney-piece and hearth are marble.
T. True. There are various kinds of it; white, black, yellow, gray, mottled and veined with different colours; but all of them are hard and heavy stones, admitting a fine polish, on which account they are much used in ornamental works.
G. I think statues are made of it.
T. Yes; and where it is plentiful, columns, and porticoes, and sometimes whole buildings. Marble is the luxury of architecture.
H. Where does marble come from?