498 



TRAP ROCKS OF THE ROWLEY HILLS. 



observed, are of different texture from most of the trap rocks described in Salop and South Wales. 

 But besides these basaltic greenstones l , there are other concretionary and amygdaloidal varieties, 

 some of which contain good specimens of other simple minerals, white calcareous spar being not 

 unfrequent. 



The relations of the Rowley Rag to the surrounding coal measures, are, as far as can be collected 

 from any evidence to be depended on, precisely similar to those which have been described in the 

 Clee Hills and other places. The trappean matter probably issued from a principal channel of 

 eruption, and in rising, cut off the coal which approaches to the sides of the hills. This is not 

 clearly seen in any openworks, but is inferred from the following data. On the western side of the 

 Rowley Hills, the carboniferous sandstone is tilted from the trap at a very acute angle, whilst the 

 colliers employed in the adjacent pits invariably stated, that the coal became of bad quality, and was 

 cut off as they worked towards the hills. The contorted, elevated, and broken condition of the 

 carbonaceous sandstones in Cawney Hill (the southern suburb of Dudley), where they are actu- 

 ally in contact with the trap, is another good proof of the disturbance created by the intrusion 

 of this rock 2 . Again, on the eastern sides of the Rowley Hills the coal was formerly worked nearly 

 to their edges, but on approaching them, the faults became numerous, and the coal was found to be 

 so deteriorated, that the pits were abandoned. One man of science, Mr. Kier, the able author 

 of the mineralogy of Staffordshire before alluded to, attempted to work coal close to the northern 

 edge of these hills, but he was compelled to resign his undertakings after much expense. Mr. 

 Yates informs us that in one of these works at a considerable distance from the hills, Mr. Kier 

 pierced a mass of greenstone 35 yards thick, and that the coal associated with it was in the state of 

 cinder. This basalt was probably so far distinct from that of Rowley as to have proceeded from 

 an independent source of eruption, for coal was wrought at lower levels and unaffected by basalt 

 between this shaft and the trappean hills. Mr. Smith is the only person I have met with who had 

 been under ground in any of the last trial pits of Mr. Kier. The galleries were driven towards the 

 hill, and he assured me that these works had been conducted to a wall of basalt, near which the 

 coal was so brittle, hard, and valueless, that the speculation was at once abandoned. Notwith- 

 standing these trials, which demonstrate that the great mass of the trap rock has issued near the 

 area where it now appears at the surface, some portions of the volcanic matter may have overflowed 

 the adjoining coal measures in a mushroom form, and in the manner described at the Clee Hills. 

 (See pp.125 et seq.) This hypothesis is supported by the circumstance, that the beds of coal re- 

 cently worked to the south-west of Oldbury, are within a few hundred paces of the trap of 

 Timmin's Hill without symptoms of derangement. Time only can determine whether the basaltic 

 matter which extends at that point as an irregular excrescence from the main ridge of trap, be 

 an overlying mass. If it is so, doubtless the coal might be worked from beneath it, as in the Clee 

 Hills. In the meantime it is proved, that the Rowley trap has pierced the coal measures subse- 

 quent to their accumulation, of which we have additional convincing proofs in the state of the coal 

 measures of Dudley Wood which are nearest to the hills ; for there the coal is not merely broken 



1 It was this basaltic greenstone (Rowley Rag), which having been fused into a perfect glass by Mr. Gre- 

 gory Watt, resumed the stony structure upon slow cooling. These admirable experiments, and others of Sir 

 James Hall, completely established the belief that basalt is an igneous product. 



4 Mr. Cartwright, an eminent surgeon of Dudley, to whose collection I shall afterwards advert, pointed out 

 to me certain trap amygdaloids which he had discovered beneath one of the streets near Dudley Church. 



