PRESTWICH — WOOLWICH AND READING SERIES. 99 



Fig. 7. — Parh Hill, Croydon. 



"■{ 



C '' 



3. London Clay (base not shown). Feet. 

 I.? Pebble beds about 10 



{c. Cla.y with Ostrea, Melania, and Cprena... „ 6 



i. Mottled clay „ 25 



a. Green sand and flint-pebbles „ 5 



III. Thanet sands „ 30 



4. Chalk. 



Owing to the number of well-sections which are necessary to trace 

 the sequence of the beds across two other Hues of section, — the one 

 S. and N. from Croydon to London, and thence to Ware, and the 

 other W. and E. from Esher to Chelmsford, — I have considered it 

 better to remove them from this part of the paper, and to place them 

 at the end, as an Appendix. 



To resume now with the sections exposed by pits at the surface, 

 eastward of the meridian of London, 



Between a line drawn from Croydon to Orpington, and the Thames, 

 is a district in which the pebble beds both of the Woolwich group and 

 of the Basement-bed of the London clay* are largely developed. 

 With the former group are constantly associated seams of fluviatile 

 fossiliferous clays and occasionally even of considerable masses of the^ 

 mottled clays. Very few sections are exposed in the central and 

 south-western portions of this district : the whole series is extremely 

 variable, and no very distinct order rules, except that on the whole 

 mottled clays (thinning out eastward) prevail in the lower part, 

 shelly beds in the central, and shingle in the upper part, but that 

 not exclusively, of this group. 



In proceeding eastward, the first sections of any consequence we 

 arrive at are in the neighbourhood of Hayes Common. Two pits 

 existed a few years since in a garden on the south side of the lane 

 leading down from that Common to Nash Farm, whilst a more recent 

 cutting made in deepening the same lane completed the section to the 

 top of the hill. This general section, which showed tolerably well 

 two zones of the Woolwich shells with the mottled clays between 

 them, is rendered in Plate I. Diag. C, Loc. sect. 19. There is also 

 a section showing the pebble beds, mottled clays, and shelly beds 

 in the lane leading down from Hayes Common towards Wickham 

 (PI. I. Diag. C, Loc. sect. 18). 



* The shingle beds of this division continue at intervals in considerable force, as 

 at Abbey Wood near Erith, Rowhill Wood Hill south of Dartford, Windmill Hill, 

 Gravesend, Shorne Hills, and Gad's Hill near Rochester. 



H 2 



