Physical Features 21 



half-way down St. Aldate's. Adjacent villages, as Marston, are on outlying 

 patches, and the Iffley and Cowley Roads follow another ; the gravel thin- 

 ning out in pockets along the Iffley Road to Fairacres. 1 



The Lowest and Last Terrace (' First ') rises only 5-10 ft. above the 

 flood level of the alluvium, and is seen as small patches of gravel ; the most 

 characteristic being that of the St. Aldate's side of Folly Bridge, taking off 

 as the second terrace gives out, and forming on the other side of the river 

 the base of New Hinksey. 2 Small banks give the foundations of Lower 

 Wolvercote, Binsey, N. and S. Hinksey, and the terrace is conspicuously 

 marked in N. Hinksey fields, part of Port Meadow, and along the river-bank 

 from Radley to Abingdon. It is largely covered by the alluvium. An 

 isolated pit at Donnington gives inferior gravel with sand 8 ft. deep, in which 

 teeth of Woolly Rhinoceros and Mammoth occur, again with stray flint 

 implements as the water-carried debris of the Thames Valley. These 

 materials may be of any age ; just as Plateau drift pebbles are found as the 

 base of the higher Terraces, and bones of the Mammoth in the alluvium 

 and gravel of Magdalen Grove. 



The River-' terraces ' are more readily visualized as sand-banks once 

 submerged, but now left high and dry with the fall of the river in the eroded 

 valley. Gravel detritus would be dropped wherever the velocity of the main 

 current was checked, as beyond a bend, spreading over flats, or where a 

 tributary stream ran into the main river at right angles. 



The Isis, cutting NE. along the Oxford Clay across the older valleys of 

 the Windrush and Evenlode, stopped all gravel coming down these tributaries, 

 forming the broad bank of gravel on the left bank of the stream (Stanton 

 Harcourt, Eynsham, Yarnton). The highest terrace is beyond the range of 

 the district at Hanborough. 



At the confluence of the Isis and Cherwell, the ' third ' terrace of Brick- 

 earth, above Wolvercote and Peartree Hill, remains as the vestiges of a sand- 

 bank, south of which the converging streams threw up the gravel-ridge of the 

 long city patch in the middle line of their course, and the line is continued 

 between the two residual streams as the 'First' Terrace of New Hinksey. The 

 fact that both the present streams of the Thames and Cherwell cut through 

 these gravels, explains the significance of the older fords at Folly Bridge 

 and Magdalen Bridge as the only spots with a gravel approach on both sides 

 of the stream. 



The Marston gravel-patch indicates a sand-bank thrown up at the con- 

 fluence of the Cherwell and the Bayswater Brook, and it is composed of 

 material from the valleys of Barton and Headington. The Donnington gravel- 

 bank is a smaller deposit at the confluence of the Bullingdon Brook and the 

 Isis, and is built up of layers of gravel with thin strata of sand from the 

 Calcareous Grit of the Bullingdon Valley. The best pit (10 ft. deep, 1921) 

 shows very distinct layering, and the gradient of some of the layers suggests 

 that the main flood-stream drove back into the valley of the tributary. 



At its widest, from Wytham Hill to Elsfield, the full stream was some 

 5 miles wide, as a flood-area narrowing to the Sandford end, where it was 

 never more than a mile wide. The stream at the ' Second ' Terrace horizon 

 was two miles wide over the City area; little over a mile at the alluvium 

 between the Castle and Botley, where it is now restricted to half a dozen 

 minor streams. 



Special interest attaches to the ' Third ' Terrace of Wolvercote, partially 

 exposed at the Brick Works, as it is largely composed of ' Brick-earth ', now 

 utilized for a special class of brick (' sand-stocks '), as opposed to the ordinary 

 poor bricks of Oxford Clay still made from the clay of the 40 ft. deep pit. 

 This ' Terrace ' is a sand-bank pure and simple, and it affords the clue to 

 1 Pocock, loc. cit., p. 87. 



a A cutting in the main road, New Hinksey (1922), which is exactly level with the river tow- 

 path, showed this gravel 20 ft. deep over the Oxford Clay. 



