ON EARTHS AND STONES. GO7 under them, is more than equal to the harm they do by taking up room. JFlints are, also, frequently found imbedded in chalk under the ground. Those used in the Staffordshire potteries chiefly come from the chalk-pits near Gravesend. So much for flints. You have seen white pebbles, which are semi-transparent, and, when broken, resemble white sugarcandy. ‘They are common on the sea-shore, and mn beds of rivers. ff, O, yes. Weeall them fire-stones. When they are rubbed together in the dark, they send out great flashes of light, and have a particular smell, “2. ‘true. The proper name of these 1s quartz. It is found in large quantities in the earth, and the ores ot metals are often imbedded in it. Sometimes it is periectly transparent, and then it is called erystal. Some of these crystals shoot into exact mathematical figures; and because many salts do the same, and are also transparent, they are called the erystals of such or such a salt. G. Is not fine glass called crystal, too? Z. It is called so by way of simile; thus we say of a thing, “it is as clear as crystal.†But the only true crystal is an earth of the kind I have been describing. Well, now we come to send; tor this is properly only quartz In a powdery state. If you examine the grains of sand singly, or look at them with a magnifying-glass, you will find them all either entirely or partly trans- parent ; and, in some of the white shining sands, the graing are all little, bright crystals. #H, But most sand 1s brown or yellowish. 7. Uhat is owing to some mixture, generally of the metalic kind. I beheve 1 once told you, that all sands were supposed to contain a small portion of gold. It is more certain that many of them contain iron. G. But what could have brought this quart. and crystal into powder, so as to have produced all the sand tm the world ? “@ That is net very easy to determine. On the oy Ad