COAL-FIELDS BROUGHT TO THE SURFACE BY UPHEAVINGS. 



507 



Mineral springs occur in the southern part of this coal-field. The most noted is a 

 collection of small wells which rise upon Pensnet Chace, and are known by the name 

 of Ladywood Spa or Cradley Salt Well 1 . In noticing this and two other saline springs, 

 the one at Brierley Hill, the other on Cradley Heath (Rowley) , Mr. Yates has well ob- 

 served, that they are situated nearly on a line, running east and west across the coal-field, 

 and coinciding with the position of a fault which extends to the south end of the Rowley 

 Hills. I have, therefore, little doubt that these springs owe their origin to disturbances, 

 which in dislocating this tract have altered the strata, from which the mineral waters 

 rise to the surface through transverse cracks or fissures. (See pp. 155, 252, and 334.) 



In reviewing the relations of the Dudley coal-field to the rocks of volcanic origin, it 

 must be remembered that the district contains two classes of trap • — the one regularly 

 interstratified and contemporaneous with the coal measures, the other injected into the 

 strata posterior to their consolidation. The former is represented by the trap-tuf, and 

 volcanic conglomerates of Haydon Hills, Corngreaves, and Hales Owen ; the latter by 

 the basalt, greenstone, and amygdaloid of the Rowley, Barrow, and Pouk Hills, &c. 

 Other phenomena teach us, that this coal-field has been subjected to violent dislocations, 

 some of which have clearly taken place since the last irruptions of volcanic matter ; for 

 it has been plainly shown, that the injected masses of trap have been broken off and 

 heaved up and down, in connection with the beds of coal with which they had previ- 

 ously been solidified. 



Thus, while the dismembered condition of this tract explains, how the sedimentary 

 deposits must have been dislocated, before the volcanic products could have risen to the 

 surface, or spread through the strata in wedge-formed masses, we also learn that the 

 region was long after the theatre of violent earthquakes (the usual followers as well as 

 precursors of volcanic action) , which have doubtless caused the great faults or fractures. 



Let it be always recollected, that such fractures have a direct practical bearing upon 

 the development of the mineral wealth of England ; for as it has been shown, that the 

 carboniferous strata of Shropshire, Staffordshire, and Worcestershire are very similar, 

 and as we know that such strata, so far from being lost at the old boundaries of the 

 coal-fields, are in general merely cut off by faults, and are continued beneath the New 

 Red Sandstone, it is highly probable, that coal measures may exist in intermediate 

 tracts, now covered by that System. At all events we know, that where volcanic 

 action has been rife, the carboniferous strata have been forced upwards through a crust 

 of red sandstone ; and hence we infer, that in those tracts where upheaving forces 

 have not acted, and the red sandstone lies in undisturbed troughs, it may cover coal- 

 fields capable of being advantageously wrought. But it must be remembered, that as 

 some of the coal-fields thus exposed are profitable and some valueless, all attempts to 



1 Mr. Cooper's analysis of the Ladywood Spa gives in a wine pint, carbonic acid 2*1, azote '4 cubic inches : 

 muriate of soda 49*75, muriate of lime 19'07, muriate of magnesia 7'50, muriate of iron 0-13, carbonate of 

 lime 1-50, carbonate of magnesia 1*70, carbonate of iron -90. 



