the equator, and the snow will not lie in that hot climate any lower down.

But now and then the snow melts off, and rushes down the mountainside in floods of water and of mud,

and the cindery cone of the volcano stands out black and dreadful against the clear blue sky, and then the people of that country know what is coming. The mountain is growing so hot inside that it melts off its snowy covering; and soon it will burst forth with smoke and steam, and red-hot stones and earthquakes, which will shake the ground, and roars that will be heard, it may be, hundreds of miles away.

And now for the words cone, crater, lava. If I can make you understand those words, you will see why volcanoes, in general, must be of the same shape as the one in the picture on the preceding page.

Cone, crater, lava: those words make up the alphabet of volcano learning. The cone is the outside of a huge chimney. The crater is the mouth of it. The lava is the ore which is being melted in the furnace below, that it may flow out over the surface of the old land, and make new land instead.

And where is the furnace itself? Who can tell that? Under the roots of the mountains, under the depths of the sea. For of the inside of this earth we know little. We only know that it is, on an average, several times as heavy as solid rock: but how that can be, we know not.

So let us look at the chimney, and what comes out of it; for we can see very little more.

Why is a volcano like a cone?

For the same cause for which a molehill is like a cone, though a very rough one; and that the little heaps which the burrowing beetles make on the moor, or which the ant-lions in France make in the sand, are all something in the shape of a cone, with a hole like a crater in the middle.

What the beetle and the ant-lion do on a very small scale, the steam inside the earth does on a great scale. When once it has forced a way into the outside air, it

tears out the rocks underground, grinds them small against each other, often into the finest dust, and blasts them out of the hole which it has made. Some of them fall back into the hole, and are shot out again: but most of them fall round the hole, many of them close to it, and fewer of them further off, till they are piled up in a ring round it, just as the sand is piled up round a beetle's burrow.

For days and weeks and months this goes on; even, it may be, for hundreds of years: till a great cone is formed round the steam outlet, hundreds or thousands of feet in height, of dust and stones, and of cinders likewise. For recollect, that when the steam has blown away the cold earth and rock near the surface of the ground, it begins blowing out the hot rocks down below, red-hot, white-hot, and at last actually melted. But these, as they are hurled into the cool air above, become ashes, cinders, and blocks of stone again, making the hill on which they fall larger and larger continually.

And why is the mouth of the chimney called a crater?

Crater, you may know, is Greek for a cup. And the mouth of these chimneys, when they have become choked and have stopped working, are often just the shape of a cup. I have seen some of them as beautifully and exactly rounded as if a cunning engineer had planned them, and had dug them out with a spade.

At first, of course, their sides and bottom are nothing but loose stones, cinders, ashes, such as would be thrown out of a furnace. But their ugliness is often covered over. I have seen craters covered with short turf, like so many chalk downs. I have seen them, too, filled with bushes, which held woodcocks and wild boars. Once I came on a beautiful round crater on the top of a mountain, which was filled at the bottom with a splendid crop of potatoes.

Often worn-out craters become beautiful lakes. There are many such crater-lakes in Italy, as you will see if ever you go there. Many such deep clear blue lakes have I seen in the Eifel, in Germany; and many a curious plant have I picked on their shores, where once the steam blasted, and the earthquake roared, and the ash clouds rushed up high into the heaven, and buried all the land around in dust, which is now fertile soil.

And long did I puzzle to find out why the water stood in some craters, while others, within a mile of them perhaps, were perfectly dry. That I never found out for myself. But learned men tell me that the ashes which fall back into the crater, if the bottom of it be wet from rain, will sometimes "set" (as it is called) into a hard cement; and so make the bottom of the great bowl waterproof, as if it were made of earth

enware.

But what gives the craters this cup-shape at first?

Think- While the steam and stones are being blown out, the crater is an open funnel, with more or less upright walls inside. As the steam grows weaker, fewer and fewer stones fall outside, and more and more fall back again inside. At last they quite choke up the bottom of the great round hole. Perhaps, too, the lava or melted rock underneath cools and grows hard, and that chokes up the hole lower down. Then, down from the round edge of the crater the stones and cinders roll inward more and more. The rains wash them down, the wind blows them down. They roll to the middle, and meet each other, and stop. And so, gradually, the steep funnel becomes a round cup.

You may prove for yourself that it must be so, if you will try. Do you not know that if you dig a round hole in the ground, and leave it to crumble in, it is sure to become cup-shaped at last, though at first its sides may have been quite upright, like those of a bucket? If you do not know, get a spade and make your little experiment.

And now you ought to understand what "cone" and "crater" mean. And more, if you will think for yourself, you may guess what would come out of a volcano when it broke out "in an eruption," as it is usually called. First, clouds of steam and dust (what you would call smoke); then volleys of stones, some cool, some burning hot; and at the last, because it lies