119 



have issued from central foci, and have been intruded laterally amid the coal 

 strata ; an opinion formerly expressed by Mr. A. Aikin in an able memoir.* 



Although these lateral masses of greenstone in the Wolverhampton field are 

 of origin posterior to the accumulation of coal strata, the author does not deny 

 that the tufaceous conglomerates of Hales Owen, which have a strong analogy in 

 composition to a certain class of volcanic grits described in former memoirs, may 

 have been formed contemporaneously with the carboniferous deposits. 



The trap of the Clent Hills is then briefly described, and is shown to be iden- 

 tical with that of the Abberley Hills, also mentioned in previous memoirs. 



5. Principal lines of dislocation. — The whole of this carboniferous tract has 

 been upcast through a cover of new red sandstone, the lower members of which 

 are frequently found to have been dislocated conformably with the inferior carbon- 

 aceous masses, proving (as formerly expressed by Mr. Murchison) that some of 

 the greatest of these movements took place subsequently to the deposits of the 

 red sandstone. In describing the faults along the boundary of the new red sand- 

 stone, he directs particular attention to that of Wolverhampton, where the coal 

 measures dip slightly inwardsirom the line of fissure, along which they are conter- 

 minous with the overlying strata, a fact, perhaps, without parallel in this or the 

 adjacent coal-fields (including Coalbrook Dale), the usual phenomena being that, 

 however disrupted, the carbonaceous or upcast strata always incline outwards, as 

 if they would pass eventually beneath the lower new red sandstone on their flanks. 

 This exception is supposed to have been caused by the upheaving of a subjacent 

 mass of Silurian or trap rocks close to the edge of the line of fault. 



Having next described the effect of the great longitudinal faults produced by 

 the upcast of the Wenlock limestone of Walsall, he shows that the subterranean 

 mass at Dudley Port, is upon the same parallel, i. e. from N. E. to S.W., if not 

 directly on the same line of fissure. This line of eruption is strongly marked on 

 both edges of the northern half of the coal-field extending to Cannock Chace. 



Another great axis of elevation which affects the Dudley field, diverges at a 

 considerable angle from the former. It is prominently marked by the line of the 

 Rowley Hills, and after concealment for a certain distance beneath the red sand- 

 stone to the S. of Hales Owen, re-appears in the ridge of the Lickey quartz rock. 

 The lofty trappean ridge of the Clent Hills is parallel to this last-mentioned axis. 

 It is further pointed out as remarkable that at the angle formed by the confluence 

 of these diverging lines of elevation, the Silurian or fundamental rocks of the tract 

 are raised in inflated ellipsoidal forms from common centres, the strata having a 

 quaquaversal dip, in one case completing the outlines of a very perfect valley of 

 elevation. The author infers that such curvatures are exactly what might be ex- 

 pected at the point of greatest flexure in the axis of the coal-field, where the volca- 



• Transactions Gcol. Soc, 1st Series, vol. iii., p. 251. 



