Coal-measures. 123 



may lie far to the east beneath the Oolitic, Cretaceous, 

 and Eocene strata of the London basin. 



The Culm -measures of Devonshire, though of true 

 Carboniferous age, and probably representing much of the 

 series, are nearly unproductive of coal. Near their base 

 there are intermittent thin streaks of limestone, which 

 may feebly represent part of the great masses of 

 Somerset and South Wales, just as the thin worthless 

 coals represent the numerous seams of these coal-fields. 

 But the conditions of deposition in the areas were 

 apparently very different. In the Devonshire area the 

 purely terrestrial intervals, marked by the growth of 

 land plants in situ, seem to have been infrequent and 

 transitory, and from bottom to top common aqueous 

 strata prevail. 



Further north, in the neighbourhood of Newent, 

 narrow bands of poor Coal-measures are barely trace- 

 able between the Old Red and the New Red Sandstones, 

 and still further north, round Bewdley, there lies the coal- 

 field of the Forest of Wyre, consisting of strata by no 

 means very productive of coal-beds. They lie directly 

 on the Old Red Sandstone, the Carboniferous Limestone 

 being absent. The Coalbrookdale coal-field joins that 

 of the Forest of Wyre, and lies partly on a thin deve- 

 lopment of Carboniferous Limestone, and partly 

 unconformably on Upper Silurian rocks. On the north- 

 west, the lower part of the New Red Sandstone is 

 faulted against it, and on the east it is overlaid by 

 Permian strata. It contains several bands of good 

 nodular ironstones, which often yield Producta, Conu- 

 laria, Orbicula, Limulus, and other marine remains, and 

 in some of the strata fossil beetles, dragonflies, and spiders 

 have been found. There are in places 22 beds of 

 coal in this field, about 10 of which are workable, some 



