Sometimes, after great rains, these piles swept away the timbers of the weir, driven by the irresistible power of the water, and then in its course the flood, carrying the balks before it like battering rams, cracked and split the bridges of solid stone which the ancients had built.  These and the iron bridges likewise were overthrown, and presently quite disappeared, for the very foundations were covered with the sand and gravel silted up.

Thus, too, the sites of many villages and towns that anciently existed along the rivers, or on the lower lands adjoining, were concealed by the water and the mud it brought with it.  The sedges and reeds that arose completed the work and left nothing visible, so that the mighty buildings of olden days were by these means utterly buried.  And, as has been proved by those who have dug for treasures, in our time the very foundations are deep beneath the earth, and not to be got at for the water that oozes into the shafts that they have tried to sink through the sand and mud banks.

From an elevation, therefore, there was nothing visible but endless forest and marsh.  On the level ground and plains the view was limited to a short distance, because of the thickets and the saplings which had now become young trees.  The downs only were still partially open, yet it was not convenient to walk upon them except in the tracks of animals, because of the long grass which, being no more regularly grazed upon by sheep, as was once the case, grew thick and tangled.  Furze, too, and heath covered the slopes, and in places vast quantities of fern.  There had always been copses of fir and beech and nut-tree covers, and these increased and spread, while bramble, briar, and hawthorn extended around them.

By degrees the trees of the vale seemed as it were to invade and march up the hills, and, as we see in our time, in many places the downs are hidden altogether with a stunted kind of forest.  But all the above happened in the time of the first generation.  Besides these things a great physical change took place; but before I speak of that, it will be best to relate what effects were produced upon animals and men.

In the first years after the fields were left to themselves, the fallen and over-ripe corn crops became the resort of innumerable mice.  They swarmed to an incredible degree, not only devouring the grain upon the straw that had never been cut, but clearing out every single ear in the wheat-ricks that were standing about the country.  Nothing remained in these ricks but straw, pierced with tunnels and runs, the home and breeding-place of mice, which thence poured forth into the fields.  Such grain as had been left in barns and granaries, in mills, and in warehouses of the deserted towns, disappeared in the same manner.