TWENTY-FIRST EVENING.

ON EARTHS AND STONES.

Tutor-George-Harry.

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? H. O yes, I do. But what is to be done to them there?

G. Why 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 mve? However, I believe we had

better ask our tutor about it. Will you please, Sir, to tell us somewhat about lime?

ago,

Tutor. Willingly. But suppose, as we talked about all sorts of metals some time 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.

H. I shall be very glad to hear it. 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 chymists use the same term for all; as, in fact, earth is only crumbled stone, and stone only consolidated earth.

H. 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, calr 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 chimneypiece and hearth are marble.

H. And so are the monuments in the church.

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? 7. From a great many countries. Great Britain produces some, but mostly of inferior kinds. What we use chiefly