WESTLETON BEDS XO THOSE OF NORFOLK, ETC. 141 



in near Coomb End at a short distance from it westward, and at a 

 level of about 100 feet lower (fig. 12). This is the most distant 

 outlier in this direction, and from its position on the edge of the 

 Chalk Downs overlooking the Great Oolitic plains, possesses more 

 than usual interest (see PI. VII. fig. 1). 



The shingle forms an ochreous sandy gravel, consisting largely of 

 subangular flints much worn, flint-pebbles, and with none of the 

 jSTew-Hed-Sandstone quartzites so common in 6'. I noted at the 

 time that it is much like the gravel on Bowsey hill (infra). 

 Approximately it was composed of : — 



per cent. 



1. Tertiary flint-pebbles, of which some were broken 44 



2. White quartz-pebbles 10 



3. Subangular and angular pieces of flint 30 



4. Subangular pieces of Sarsen stone, of a hard dark sandstone, 



and of ironstone (Tertiary) 9 



5. Flat ovate pebbles of light-coloured quartzite, with small pebbles 



of Lydian stone (?), and of a quartz-grit 7 



100 



I failed to note either Chert or Kagstone. 



A few miles to the south another Tertiary outlier extending 

 from Chazey Heath to Eose Hill (300 to 350 feet) is capped, but not 

 very distinctly, by a light-coloured gravel very similar to the above, 

 while the intermediate and lower areas are overspread by the Glacial 

 gravel, but Boulder- clay is absent. 



Further to the soath, as we approach the Thames, the valley- 

 gravels set in and continue to the Berkshire side. 



BerJcshire and Wiltshire. — Between Reading and Maidenhead * 

 the broad valley of the Thames, with its Post-Glacial gravels, 

 becomes greatly contracted between Henley and Marlow by the 

 high ground of Cookham Dean (350 ? feet) and Bowsey Hill, which 

 is 467 feet high, or 350 feet above the Thames at Henley. The 

 former of these hills is bare to the summit, whereas the latter is 

 capped by a light ochreous sandy and pebbly gravel, from 5 to 8 

 feet thick, of a characteristic Westleton type. The following are 

 its component parts, but I failed to note their relative proportion : — 



1. Tertiary flint-pebbles, some of them entirely decomposed. 



2. Nxmierous small white quartz-pebbles. 



3. Subangular fragments of flint, weathered white. 



4. Very few subangular fragments of white ragstone and one of fossil- 



iferous chert. 



5. Pebbles of light-coloured quartzite. yellow sandstone, and rose-coloured 



quartz-grit, with some small pebbbs of veinstone, I/ydian or hornstone, 

 greenstone?, and red and grey quartz. 



The quartzites are not the red and grey quartzites of the northern 

 Drift. 



* It would seem probable that the Thames at an early stage may have 

 flowed in a direct line from Twyfbrd to Maidenhead, by way of tlie valley of 

 White Walthani, which offers a low and straight course, instead of (he ciriMiitous 

 com'seit took in Post-Glacial times through the Henley and Cookham Hills. 



