The question arises, Why should these two ranges of hills, the Marlborough Downs and the Chiltern Hills, meet just at this point? Is it simply an accident of geography that their two ends stand exactly face to face on opposite sides of the Thames? Now the geologists tell us that it is no coincidence. They have studied the strata—that is, the different layers of the materials forming the hills—and they find that the strata of the range on the Berkshire side compare exactly with the strata of the other; so that at some remote period the two must have been joined to form one unbroken range. How then did the gap come? Was it due to a cracking of the hill—a double crack with the earth slipping down in between, as has sometimes happened in the past? Here again the geologists tells us, No. Moreover they tell us that undoubtedly the River has _cut its way_ right through the chalk hills. “But how can that be possible?” someone says. “Here we have the Thames down in a low-lying plain on the north-west side of the hills, and down in the valley on the south-east side. How could a river flowing across a plain get up to the heights to commence the wearing away at the tops?” Here again the geologists must come to our aid. They tell us that back in that dim past, so interesting to picture yet so difficult to grasp, when the ancient, mighty River flowed (see Book I., Intro.), the chalk-lands extended from the Chilterns westwards, that there was no valley where now Oxford, Abingdon, and Lechlade lie, but that the River flowed across the top of a tableland of chalk from its sources in the higher grounds of the west to the brink at or near the eastern slope of the Chilterns; and that from this lofty position the River was able to wear its way down, and so make a =V=-shaped cutting in the end of the tableland. Afterwards there came an alteration in the surface. Some tremendous internal movement caused the land gradually to fold up, as it were; so that the tableland sagged down in the middle, leaving the Marlborough-Chiltern hills on the one side and the Cotswold-Edgehill range on the other, with the Oxford valley in between. But by this time the =V=-shaped gap had been cut sufficiently low to allow the River to flow through the hills, and to go on cutting its way still lower and lower. CHAPTER FOUR _Reading_ Reading is without doubt the most disappointing town in the whole of the Thames Valley. It has had such a full share of history, far more than other equally famous towns; has been favoured by the reigning monarch of the land through many centuries; has taken sides in internal strife and felt the tide of war surging round its gates; it has counted for so much in the life of England that one feels almost a sense of loss in finding it just a commonplace manufacturing town, with not a semblance of any of its former glory.