THE THAMES AT SINODUN HILL
Fresh water is almost the oldest thing on earth. While the rocks have been melted, the sea growing salter, and the birds and beasts perfecting themselves or degenerating, the fresh water has been always the same, without change or shadow of turning. So we find in it creatures which are inconceivably old, still living, which, if they did not belong to other worlds than ours, date from a time when the world was other than it is now; and the fresh-water plants, equally prehistoric, on which these creatures feed. Protected by this constant element the geographical range of these animals and plants is as remarkable as their high antiquity. There are in lake Tanganyika or the rivers of Japan exactly the same kinds of shells as in the Thames, and the sedges and reeds of the Isis are found from Cricklade to Kamschatka and beyond Bering Sea to the upper waters of the Mackenzie and the Mississippi. The Thames, our longest fresh-water river, and its containing valley form the largest natural feature in this country. They are an organic whole, in which the river and its tributaries support a vast and separate life of animals and plants, and modify that of the hills and valleys by their course. Civil law has recognised the Thames system as a separate area, and given to it a special government, that of the Conservators, whose control now extends from the Nore to the remotest springs in the hamlets in its watershed; and natural law did so long before, when the valley became one of the migration routes of certain southward-flying birds. Its course is of such remote antiquity that there are those who hold that its bed may twice have been sunk beneath the sea, and twice risen again above the face of the waters. It has ever been a masterful stream holding its own against the inner forces of the earth; for where the chalk hills rose, silently, invisibly, in the long line from the vale of White Horse to the Chilterns the river seems to have worn them down as they rose at the crossing point at Pangbourne, and kept them under, so that there was no barring of the Thames, and no subsequent splitting of the barrier with gorges, cliffs, and falls. Its clear waters pass from the oolite of the Cotswolds, by the blue lias and its fossils, the sandstone rock at Clifton Hampden, the gravels of Wittenham, the great chalk range of the downs, the greensand, the Reading Beds, to the geological pie of the London Basin, and the beds of drifts and brick earth in which lie bedded the frames and fragments of its prehistoric beasts. In and beside its valley are great woods, parks, downs, springs, ancient mills and fortresses, palaces and villages, and such homes of prehistoric man as Sinodun Hill and the hut remains at Northfield. It has 151 miles of fresh water and 77 of tideway, and is almost the only river in England in which there are islands, the famous eyots, the lowest and largest of which at Chiswick touches the London boundary.
After leaving Oxford the writer has lived for many years opposite this typical and almost unspoilt reach of the London river, and for a considerable time shot over the estate on the upper Thames of which Sinodun Hill is the hub and centre. This fine outlier of the chalk, with its twin mount Harp Hill, dominates not only the whole of the Thames valley at its feet, but the two cross vales of the Thame and the Ock. On the bank opposite the Thame joins the Isis, and from thence flows on the THAMES. Weeks and months spent there at all seasons of the year gave even better opportunities for becoming acquainted with the life of the Upper Thames, than the London river did of learning what the tidal stream really is and may become. Fish, fowl and foxes, rare Thames flowers and shy Thames chub, butterflies, eel-traps, fountains and springs, river shells and water insects, are all parts of the "natural commodities" of the district. There is no better and more representative part of the river than this. Close by is Nuneham, one of the finest of Thames-side parks, and behind that the remains of wild Oxfordshire show in Thame Lane and Clifton Heath. How many centuries look down from the stronghold on Sinodun Hill, reckoning centuries by human occupation, no one knows or will know. There stands the fortress of some forgotten race, and below it the double rampart of a Roman camp, running from Thame to Isis. Beyond is Dorchester, the abbey of the oldest see in Wessex, and the Abbey Mill. The feet of the hills are clothed by Wittenham Wood, and above the wood stretches the weir, and round to the west, on another great loop of the river, is Long Wittenham and its lovely backwater. Even in winter, when the snow is falling like bags of flour, and the river is chinking with ice, there is plenty to see and learn, or in the floods, when the water roars through the lifted hatches and the rush of the river throbs across the misty flats, and the weeds and sedges smell rank as the stream stews them in its mash-tub in the pool below the weir.
 Phillips, "Geology of Oxford and of the Valley of the Thames."