TRANSACTIONS OF SECTION C. 730 
aggregate thickness of 212 feet of workable coal. That of Mons is 9,400 feet with 
110 seams yielding 250 feet of coal. In Somersetshire the coalfield is 8,400 feet 
thick, the seams are fifty-five in number, and yield 120 feet of available coal. It is 
obvious from these figures that the possibilities of the South-eastern coalfield are very 
great, although it still remains to be proved how far these great thicknesses of rock 
haye been denuded in Kent before the deposition of the Triassic and Jurassic rocks. 
The upper denuded surface of the South-eastern field was struck at Ropersole 
at a depth of 1,373 feet 7 inches below Ordnance datum, and at Dover at 
1,100 feet 6 inches. If the rocks which have to be traversed above O.D. be 
added, the resulting figures of about 1,600 feet necessary to sink from the surface 
are well within the depth to which coal is now being worked at a profit in 
England and in France and Belgium. The coal is well within the 4,000-feet limit 
laid down by the Coal Commission of 1872. 
The strata overlying the coal measures at Ropersole and Dover present points 
of great geological interest bearing on the geographical conditions under which 
they were formed, as may be seen from the following table :— 
Table of Comparative Thicknesses of Neocomian and Jurassic Rocks 
at Dover and Ropersole. 
— Dover Ropersole 
| ft. in, ft, in, 
Neocomian - . d : ; ci | 124 8 72 O 
Purbeck-Wealden . P F ; c ‘ 94 6 55 0 
Oolitic . ; ; : : : ; 51) “ S 472 0 
SG AS ee a ees aoe i Be 27 9 
All these rocks are thinning off to the northwards against the carboniferous and 
pre-carboniferous rocks, which form the ‘ axis of Artois’ of Godwin-Austen, as he 
foresaw in 1858 that they must thin off in South-eastern England. South and 
west of the meridian of Dover they thicken very rapidly, the Neocomians being 
244 feet, the Purbeck-Wealden of Kent and Sussex being not much less than 
2,000 feet thick, and the Jurassic rocks of considerable though unknown thickness. 
In the Netherfield boring, near Battle in the Hastings district, the Upper and 
Middle Oolites are proved to be more than 1,700 feet thick. 
The evidence of the other boreholes under my supervision proves that the 
thickening of the Neocomian, Purbeck-Wealden, and Upper Jurassic strata to the 
south of the downs between Folkestone and Tonbridge is very considerable. 
It is summed up in the following table :— 
— | Ottinge | Hothfield | Old Soar | Penshurst 
Neocomian . : , A ; - 246 180+ | 250 
Purbeck-Wealden - 3 146 593 | 650 1,511 
Portlandia a peice. «i 2 i — | : — 
| Kimmeridge Clay. : : ; — — | — 356 + | 
The Purbeck-Wealden beds also show a considerable thickening to the west, 
if the boring at Ottinge be compared with that of Penshurst, near Tonbridge, 
where the boring began low down in the Ashdown Sand, the lowest member but 
one of the group. yh : 
Tt remains for us to sum up the results of these borings, which are likely to 
effect the same economic revolution in Kent as was brought about in France 
by the extension of the coalfield of Valenciennes and Mons, about ninety-five 
miles to the west of its original outcrop at the surface, and to within some thirty 
miles of Calais. The coalfield has been proved at Dover. Its range for eight miles 
to the north has been also proved at Ropersole. Its southern boundary, as yet ill- 
defined, is marked by the Pembroke-Mendip anticline, ranging under the southern 
1899, 3B 
