TRAP ROCKS OF THE DUDLEY COAL-FIELD. 



497 



104. 



View of the Pearl Quarry, Timmin's Hill {Rowley). 



Trap Rocks of the Dudley Coal-Field. 



The earliest rocks of igneous origin connected with this coal-field, are the bedded 

 volcanic grits to which I have already alluded in describing the strata, p. 471. The 

 other class of trap, which is of subsequent date, appears at various detached points 

 through the coal-fields of Dudley and Wolverhampton. The largest mass in that neigh- 

 bourhood constitutes the stony hills, extending from Rowley Regis to the southern 

 suburbs of Dudley, having a length of upwards of two miles and a width of about one 

 mile. 



These hills range from 15° W. of N., to 15° E. of S., as may be well seen on their western 

 edge, and they are termed in succession, Cawney, Tansley, Warren, Turner, Hailstone, Hawes and 

 Highnam Hills. On their eastern side Cox's Rough and Timmin's Hill are the most prominent 

 points, whilst the church of Rowley is built upon the culminating point of the rock near its 

 southern termination. These hills have long afforded roadstone for the use of the surrounding 

 country, under the name of " Rowley Rag." It is usually a hard, fine-grained, crystalline 

 greenstone, in some cases approaching very nearly to basalt, being an intimate admixture of grains 

 of hornblende with small crystals of felspar and a few grains of quartz. One of the most precipi- 

 tous faces of the rock is seen at the Hailstone near Rowley, where broad prismatic masses, of a grey 

 colour, rise on the west sides of the hill, and within a few hundred paces of some old coal-pits, the 

 intervening slope being strewed with broken blocks of the greenstone. In this rock the felspar is 

 intimately mixed with the hornblende, but the facets of the crystals of the latter glisten upon fresh 

 fracture. 



A most beautiful example of the slender columnar form is seen at the Pearl Quarry in Timmin's 

 Hill, as represented in the above wood-cut, where prisms not less than thirty feet in length and of 

 a few inches only in width, are exposed in a quarry. In Tansley Hill, there are fine examples of 

 convergence and divergence of similar slender prisms. Some varieties of these rocks, it will be 



