If we ask an astronomer how our World came into existence, he will tell us that it is probably a mass separated from the Sun, that it was once red-hot, and that it slowly cooled down until animals and plants could live upon it. He will tell us besides, that he can see mountains and valleys in our Moon, and land and sea, snow and clouds, on the planet Mars, with his great telescopes. When he thinks about the planets and our own World, then he believes them to be pieces of some much larger World—perhaps the Sun—which now travel round the Sun and receive their light and heat from it. The World is made of what we call “earth,” and it is of this I mean to tell you now—how it was formed, what changes have taken place in it, what plants and animals have lived upon it, and what reasons there are for thinking that it is an exceedingly old place, with a long and interesting story to tell. Little was known thirty or forty years ago by the most learned men about the age of our World, and it was thought that the human race had not lived here very long. It was indeed known that many large animals, whose huge bones have been found, must have lived before man came to inhabit the Earth, and that even far smaller creatures—such as fishes, and crabs, and insects, and shell-fish—most probably lived for many generations, and died and left their bones and shells in the soil long before the first man or the first tribes of men came to share the World with them. I hope to be able to tell you something of the strange and beautiful history of all these animals, and of man himself, and to show you what reasons there are now for thinking that the human race has inhabited this Earth for a very long time indeed, and how all this knowledge has been gained and put together piece by piece. It is something like the different parts of a puzzle-map, which might be scattered all over the house, and found at one time or another in different places, and at last made up altogether. Some parts of the puzzle have not been found yet certainly; but so many have been collected, and they fit into one another so well, that we can begin to see its real shape and size. It will perhaps be a very long time before some of the missing pieces are found; but in the meantime we can go on without them, and put the framework together, and no doubt in time we shall see what our puzzle, the history of life on the Earth, was like.