The first thing that we know about man on the earth is what we know by finding the weapons or tools that show signs of his handiwork. It is one of the most distinguishing marks of man, setting him most clearly apart from all other animals, that he has been a maker of tools and weapons for an immense number of years. Intelligent though some dogs and monkeys and other animals are, not one of them has thought of doing this. The oldest sort of tools or weapons that we find are made of stone, generally of flint, chipped to a sharp edge or point, so as to make axe or spear-head. We know them to be older than any of the metal tools or weapons that we find, because we find them in a deeper layer, or stratum, of the earth--a stratum deposited before those which lie above it. And we find them in company with fossil remains of animals which are {6} of less-developed species than those in the strata above. [Sidenote: Man's tools and weapons] After a while--an immensely long while--there can be little doubt that man discovered that the ore of metals, which is found in the ground, can be fused, that is to say, melted by fire; that it can be separated from its earthy surroundings, and so be made useful. Man then began to make weapons and implements of metal, and found them better than the weapons of stone. We may infer this from the fact that the stone implements, of sharp and shapen flint, become less numerous as we come to higher strata, or layers, in the ground, and the metal implements are more numerous. The metal of which the earliest metal implements were made is either pure copper or bronze, which is a mixture of copper and tin. Copper is not a very hard metal. I suppose that the more tin that was put into the mixture, in comparison with the copper, the harder it would be. And then, after a while--again a very very long while--man discovered another, a harder, and therefore a better, kind of metal, that is to say iron. And he has never found a better metal in all the long years of his story since. Gold and platinum may be more precious, because they are less common; but iron is a great deal more useful to man. His weapons, his swords, bayonets, and cannons are made of it; so are his ships; and you hardly can open your eyes in a room without their resting on something made of iron. As soon as he had found out the hardness of iron we may suppose that man quickly gave up the use of the soft bronze, as he had formerly given up the use of the stone in favour of the bronze. Thus it comes that you may read of the Stone Age, the Bronze Age, and the Iron Age. They refer to these three stages {7} in man's history: first, when he was using stone implements, made of the chipped flint or the like hard stone; second, when he was using the bronze weapons and tools; and third, when he was using iron.