178 Professor W. Boyd Datokins [June 6, 



boiiuclary is the line of the Mendip Hills. They also probably occur 

 at a depth which remains to be proved, still further to the south, in 

 the valley of the Axe and the district of Glastonbury, the most 

 southern boundary being the mountain limestone of Cannington, near 

 Bridgwater (see map). The great Somerset and Gloucester held may 

 extend to the east under the newer rocks, between Freshford and 

 Beckington, in the district south of Bath. 



The value of the evidence of the coal-fields of the West of 

 England on the general question consists in the fact that they may 

 be taken as fair samples of those which lie concealed along the line 

 of the buried ridge through South-eastern England in the direction 

 of France, Belgium, and Germany. 



7. One of these concealed coal-fields has been struck in a deep 

 boring at Burford, near Witney, in Oxfordshire, at a depth of 

 1184 feet, under the following rocks: — 



Oolites 148 feet. 



Lias 598 „ 



Ehoetic 10 „ 



Triassic rocks 428 „ 



The sandstones and shales of the coal-measures were penetrated to a 

 depth of 225 feet.* 



These coal-measure rocks form, as suggested by Hull, one of the 

 same series of coal-basins as those of South Wales and the Forest of 

 Dean, and probably mark the line of the continuation of the South 

 Wales syncline in the direction of Harwich, where Carboniferous 

 shale has been struck at a depth of 1052 feet from the surface. 



This boring proves not merely the presence of coal-measures at a 

 workable depth in Oxfordshire, but also the important fact that the 

 Triassic rocks, which are of great thickness further north, have 

 dwindled down to an unimportant thickness in their range south- 

 wards and eastwards. Further, that south, in the London area, these 

 rocks are wholly absent ; and farther to the east, at Harwich, the 

 Liassic and Oolitic strata and Lower Greensand are absent, and the 

 Gault rests on the eroded Lower Carboniferous rocks, inclined at a 

 high angle. 



8. The water-worn surface of the folded rocks, which are older 

 than the Carboniferous, has been repeatedly struck in deep borings 

 for water in the neighbourhood of London, at depths ranging from 

 839 feet at Ware to 1239 feet at Richmond. They consist of Silurian 

 strata in the north at Ware, and of Old Red Sandstone or Devonian 

 rocks in the other localities. From their high angle of dip, as in 

 the case of similar rocks underlying the coal-fields of Somerset and 

 Northern France and Belgium, it may be inferred that coal-fields lie 

 in the synclinal folds in the neighbouring areas. 



From the fact of the Silurian rocks being in the north, while all 



* De Kance, Mauch. Geol. Soc, 20th March, 1878. 



