504 Professor W. Boyd Daichins—Tlie S.E. Coalfield. 



seams yielding 250 feet of coal. In Somersetsliire 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 

 have 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 1,180 feet 9 inches below Ordnance datum, 

 and at Dover at 1,100 feet 6 inches. If the j-ocks 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. It is well within the 4,000 feet limit laid 

 down by the Coal Commission of 1872. 



The strata overlying the coal-measures at Eopersole and Dover 

 present points of great geological interest beai-ingon 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 E,opeusole. 



Neocomian . . . 

 Purbeck-Wealden 

 Oolitic 

 Liassie 



Dover. 



ft. in. 



124 8 



94 6 



634 10 



Eopersole. 



ft. in. 



72 



55 



473 



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 

 tin known 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. 



HothSeld. 



Old Soar. 



Penshurst. 



Neocomian... 



Purbeck-Wealden 



Poitlandian 



Kimmeridge Clay 



246 

 146 



180 + 

 593 



?50 

 65U 



1,511 

 356 + 



