EFFECTS OF THE MEETING OF TWO LINES OF ELEVATION. 



505 



Dudley,) elevates certain detached masses of Silurian rocks. To the south of Dudley, 

 the same line, bending 5° or 10° more to the east, is still more powerfully marked by 

 the outburst of the great trappean ridge of the Rowley Hills. An axis of elevation, 

 proceeding from the southern end of these hills, is further traceable, through the arched 

 and anticlinal forms of the tufaceous conglomerate and sandstone east of Hales Owen. 

 (See Map.) It is also on this great and long line of dislocation, or on a fissure precisely 

 parallel to it, that the Silurian strata of the Lower Lickey have been elevated, the short 

 interval of about three miles, which separates those rocks from the dislocated coal 

 measures, near Hales Owen, being concealed by the Lower New Red Sandstone. And, 

 lastly, the trap of the Clent and Lickey Hills, has also been erupted on the same parallel, 

 as the axis of the Dudley and Rowley Hills and the Lickey quartz ridge. 



Looking, therefore, at the general configuration of this tract, extending from Cannock 

 Chace to the Lower Lickey Hills, we see that the Silurian rocks which support the coal 

 measures, have been thrown into divergent directions by two separate lines of elevation ; 

 and these divergences have, we presume, been determined by the eruptive forces which 

 evolved the trap rocks, because we find the latter bursting out and dislocating the strata 

 on both these lines. We might naturally expect, that the points of meeting of these 

 divergent lines should be marked by peculiar phenomena, and such is the case ; for the 

 singular domes or ellipsoids of elevation in the Silurian rocks north of Dudley, where 

 the strata have undergone every degree of curvature and fracture, are situated exactly 

 where the lines of eruption cross each other. Here, it is presumed, the heat and 

 gaseous accompaniments of volcanic operations, unable to escape, have been the chief 

 cause of these inflated forms, as well as of those of similar shaped and altered ridges of 

 Caradoc sandstone near the Lickey Hills. 



But besides the great lines of dismemberment which have determined the outline of 

 the carboniferous tract, and have partially thrown up the Silurian rocks once subjacent 

 to it, there are many considerable transverse fractures, or, as they are called, east and 

 west faults. Some of these have already been alluded to, both north of Wolverhampton 

 and between Dudley Port and Wednesbury. The '•' Lanesfield fault,' 5 one of great mag- 

 nitude, proceeds from near the northern termination of the Sedgeley Hills, almost to 

 Wednesbury, a distance of about three miles. This fault, it will be perceived, ranges 

 precisely from the point where the north-east and south-west line of elevation is met 

 by that which strikes to the east of south, and is, therefore, just such a cross fracture 

 as might naturally take place, during the heaving up of solid masses into divergent 

 directions. 



That transverse cracks would follow from elevations of tracts ''en masse" has recently 

 been sustained upon mathematical and mechanical principles by Mr. Hopkins 1 ; and 



1 Trans. Cambr. Phil. Soc, vol. vi. p. 1. The memoirs of Mr. Hopkins are full of profound mathematical 

 and mechanical knowledge, and may eventually lead to an explanation of some of the most recondite principles 

 of geology. 



