1876.] 
307 
Geological Formations of the Central and S.E. Counties. 
Thickness in Feet. 
Formations. 
1. 
2 . 
3 I 
4. 
5- 
6 . 
7- 
8 . 
9 - 
10. 
11. 
12. 
13-1 
14. 
London Clay 
Lower Tertiary (sands and pe 
ble beds) 
Chalk.. .. .. .. .. 
Upper Greensand .. 
Gault Clay 
Lower Greensand* * * § .. 
Purbeck and Portland beds 
Kimmeridge Clay 
Coral Rag and Grit . . 
Oxford Clay 
Great and inferior Oolites 
Upper Lias Sands . . 
Upper Lias Clay 
Marlstone, or Middle Lias 
Lower Lias Clay 
Reaper Marls (Trias.) f . . 
Lower Keuper Sandstone): .. 
New Red Sandstone (Bunter)|j 
Lower Permian Beds (alter- ) 
nating characters) . . . . J 
Permeable 
Impermeable 
Quality of 
Strata. 
Strata. 
Water. 
— - 
150 to 280 
— 
70 to IOO 
— • 
Soft. 
645 to 1000 
- — 
Hard. 
100 to 400 
130 to 200 
Rather hard. 
20 tO 500 
— 
Soft & good. 
0 to 60 
300 
Rather hard? 
40 
350 to 400 
Rather hard. 
200 tO 45O 
- — 
Hard. 
20 tO 200 
— 
Soft ? 
— 
30 to 300 
— 
30 to 250 
— 
Rather hard ? 
500 to 600 
600 to 3000 
Gen’ly imper. 
150 to 450 
— - 
Soft. 
0 to 2150 
— 
Soft or variable. 
Variable. 
Variable. 
Soft. 
Thus out of the fourteen sets of strata arranged in the 
above table according to their water-bearing qualities, there 
are eight which are permeable, viz., (2) the Lower Tertiary 
Sands, (3) Chalk and Upper Greensand, (5) Lower Green- 
sand, (6) Purbeck and Portland beds, (8) Coral Rag and 
Grit, (10) Oolites and Upper Lias Sands, (12) Middle Lias, 
(14) New Red Sandstone, with a total thickness varying 
from 1275 to 5600 feet ; while there are, alternating with 
the above, six sets of strata which are impermeable, viz., 
(1) London Clay, (4) Gault Clay, (7) Kimmeridge Clay, 
(9) Oxford Clay, (11) Upper Lias Clay, (13) Lower Lias and 
Keuper Marls, with a total thickness varying from 2110 to 
5030 feet vertical. § 
* The Lower Greensand of Surrey consists of several members of varying 
hydrometric qualities, for an account of which see “ Geology of the Straits of 
Dover,” by W. Topley, F.G.S., and “ Horizontal Wells,” by W. Lucas, p. 21. 
f The beds of Keuper Sandstone about the centre of the mails often contain 
water. In the Scarle boring, a feeder of water yielding n gallons per minute 
was r truck in these beds, at a depth of 790 feet. 
J In Scarle boring, about 250 feet thick. 
|| Scarle, 540 feet. 
§ I have purposely omitted the clays and gravels of the drift-series, as they 
are of so variable a nature that no general rule can be laid down regarding 
their water-bearing qualities. The boulder clay is, however, a generally im- 
permeable stratum, and the middle sands and gravels, water-bearing ; from 
these springs of good soft water often issue forth. 
2 G 2 
