The Stone Age is beyond all history, the Bronze begins with it, and the Iron Age began at some distant time before the dawn of authentic history. Thus we are told, in Genesis iv. 22, that Tubal Cain taught people to make it. It was used also by the Egyptians for perhaps 2,000 years before the Christian era; but the real Iron Age is that in which we are living now. We can, indeed, make all metals much better than any of the older nations. But there is a wide gap between the time when people left off using stone and discovered bronze and iron; and if one of the Druids could come to life he might help us to fill it up, because those old British priests had many secrets, which they told to one another from generation to generation. If the Spanish conquerors had not destroyed the civilization of Mexico and Peru, we might know something of the discovery of the metals there, and the people of India and China must have used them long ago; but the first use of metal in any country where it was found out would most likely be before the people had begun to put their language into any kind of writing, so that the time would be forgotten among the many scraps of lost knowledge which we have tried to collect from the remains of the industry of pre-historic man. We have seen how much these ancient people differed from us in their civilization, and how far they were behind us in everything; but we must not suppose that they were very different in bodily size and shape. Some of their skulls might have belonged to a philosopher, or they might have contained the thoughtless brains of a savage. The skulls from the Cromagnon and Engis caves are quite equal in size and shape to those of several uncivilized, and even of some civilized races of the present time, and there are people in all large cities whose heads are not better formed. Though the outward signs of their civilization then were so different from ours, it is not certain that their mental capacity was much less.