As time passed they began to make improvements in their houses. The first improvement seems to have been to build walls, up to about the height of a man's head--timber walls only at first--making use of trunks that had grown with a bend in them, as the corner posts, for the arch. From that came the occasional use of stone for the walls, where stone was easily to be found, or of brick, where there was clay convenient for the baking; but for very many years wood was the usual material for the building of all except the great houses, churches, castles, and the like. Of course it was very inflammable, and you know how, even as late down in our story as the date (1666) of the great fire of London, the destruction was so complete because almost all the houses were of wood. {106} CHAPTER XIII HOW THE PEOPLE LIVED--_continued_ It is likely that some of the Celts, before the coming of the later invaders, had begun to descend from their hill villages and to occupy the river valleys and clearings in the woodlands; but we do not know much of their story, and have to piece it together as best we may from the signs of their residence which they have left. Both before the Roman occupation of Britain and also for two or more centuries afterwards, we do not know at all clearly what went on in our island. But about the Saxons, nearly from their first coming to England, we have written evidence to give us information. We know something of how their village societies were formed, and these societies are extremely interesting to us, because we can see from them how our present way of living came about, how the landowner and the tenant, the squire and the agricultural labourer came to be. [Sidenote: How people lived] The villages, then, in these Saxon times, consisted of a group of the "wattle and daub" houses formed in the manner that you have seen. If they were built near one of the roads, the houses would be on either side of the road, forming something like what we call "the village street" now. If they were not near a road they would often be arranged in a circle, with a clear space in the middle. In this clear space, surrounded by the houses, we may see the earliest form of the modern "village green." {107} And then, outside the circle of houses would be the lands which the villagers held and worked. There would be a certain area of this land which would be cultivated, with the plough, for crops, and, further, outside that there would be land which would be grazed by the villagers' cattle and sheep. It would be what we call "common land," and any freeman in the village would have the right to turn out on it a certain fixed number of animals. Besides this there would be a certain area of ground beyond again, called "the waste," where the pigs of the villagers might be turned out to feed in the woods. This area also was defined by law, so that it should not run into the area allotted to a neighbouring village.