If you watch the little rills of water on any rainy day, trickling down a hill, or the springs which bubble up at the foot of cliffs on the sea shore, you will see an example of denudation in a small way. The earth is washed off the surface here and there, and carried down and laid up in banks in some places, and the harder ground underneath is laid bare. Little beds of stones are collected in one place, and sticks and straws and such light things in another, and this is just what has been done on a large scale in mountain regions, all over the world for many centuries. In the uppermost sketch on page 51 you will see how the granite has been lifted up with the layers of other earth along its sides, and afterwards even layers have been deposited above; in the second there has been a great crack in the land, and a great mass of rock has subsided, and the hollow has become filled up in time with clay, and mould, and rich soil, so that some one has built a house and made a garden on it; in the third the river has cut a gorge in rocks which were once continuous from cliff to cliff, wearing away the softer earths more easily than the harder. If the Earth was cut into in different places we should find the rocks arranged in a very similar way to that in the three sketches. BOILING SPRINGS, ETC. In several different countries there are very strange sights, but scarcely anything is more astonishing than the fountains of boiling water which shoot up out of the ground. There are a good many of them not far from us, in Iceland, and many hundreds in Wyoming in America, and they are called “geysers.” Steam and boiling water, and sometimes mud, are thrown up by these natural fountains to a height of 200 feet—as high as the top of the spire of a church. The water must come from a great depth in the ground—perhaps many thousand feet down—where the heat is intense. This water springing up with clouds of snow-white steam, and falling all round in showers, has a most beautiful appearance. These geysers now and then throw out very little water, just bubbling up above the ground, and then travellers boil eggs and chickens and such things in them, and have a pic-nic near them. It is impossible to say how long they have lasted, but we know from history that some have been spouting out water for at least 2,000 years, and how much longer no one can tell. They may have something to do with volcanoes, because water may have found its way to the heated interior of the earth, and being converted into steam, expands and causes an eruption. Now that we have some idea of the construction of the Earth, we must go on to the _life_ of the wonderful plants and creatures which have peopled it. _THE VEGETABLE PART._ THE DAWN OF LIFE.