49 1 Geological Sociel^, 



numerous where the mass is much altered, as almost to obscure the 

 true laminae of deposit. 



4. Trap. — The composition and characters of the trap rocks and 

 basaltic masses of the Rowley Hills are first described, together with 

 the manner in which they are supposed to rise through and cut off 

 the coal u|)on their flanks. Rocks of similar origin occur at various 

 detached points to the west of Dudley, of which Barrow Hill is the 

 principal, affording the most convincing proofs of the volcanic mass 

 having burst through the carboniferous strata, since the latter are not 

 onlv highly disturbed and broken, but fragments of coal and coal mea- 

 sures, in highly-altered conditions, are found twisted up upon the sides, 

 and even mixed with the trap itself. In the ^Volverhampton or north- 

 ern coal-field, the chief vent of eruption is atPouk Hill, two miles west 

 of Walsall, where the greenstone is arranged in fan-shaped columns. 

 After pointing out distinct evidences of the intrusion of similar rocks 

 at Bentley Forge and the Birch Hills, in some of the old open works 

 near which the trap is seen to overlie the coal, the author gives vari- 

 ous sections of subterranean works, which prove the existence of 

 greenstone, in bands more or less horizontal. As these bands of trap 

 have jagged edges, are of limited extent, of exceeding irregularity 

 in thickness, and often produce great alteration upon the inclosing 

 carbonaceous masses, the author has no hesitation in expressing his 

 belief that tliey are not true beds, but simply wedges of injected matter 

 which 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 vol- 

 canic grits described in former memoirs, may have been formed con- 

 temporaneously with the carboniferous deposits. 



The trap of the Clent Hills is then briefly described, and is shown 

 to be identical with that of the Abberley Hills, also mentioned in pre- 

 vious memoirs. 



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

 has been upcast through a cover of new red sandstone, the lower mem- 

 bers of which are frequently found to have been dislocated conform- 

 ably with the inferior carbonaceous masses, proving (as formerly ex- 

 pressed by Mr. Murchison) that some of the greatest of these move- 

 ments took place subsequently to the deposit of the red sandstone. In 

 describing the faults along the boundary of the new red sandstone, he 

 directs particular attention to that of Wolverhampton, where the coal 

 measures dip slightly inwards from the line of fissure, along which they 

 are conterminous with the overlying strata, a fact perhaps without 

 parallel in this or the adjacent coal-fields (including Coalbrook Dale), 

 the usual phsenomena being that, however disrupted, the carbonaceous 

 or upcast strata always incline outwards, as if they would pass even- 

 tually beneath the lower new red sandstone on their flanks. This 



* Transactions Geol. See, 1st Series, vol. iii. p. 251. 



