296 



LINES OF ELEVATION IN THE NEW RED SANDSTONE. 



the accuracy of the conjecture 1 . In the previous account of the Breidden Hills, it has been shown 

 that the trap forms two principal parallel ridges ranging from W.S.W. to E.N.E., viz. Moel-y-Golfa 

 and its dependent hills extending to Bauseley on the S.S.E., and the Breidden, properly so called, 

 on the N.N.W. In these ridges it has also been shown that there are evidences of two periods of 

 eruption. 1st, Of contemporaneous trap, alternating conformably in thin bands with schists of the 

 Silurian System. 2ndly. Of intrusive trap, which bursting through the former, has thrown the strata 

 into vertical and dislocated positions, altering them and producing veins more or less metalliferous. 

 Besides the Silurian rocks and bedded trap rocks affected by these eruptive masses, there are indica- 

 tions on the flanks of Bauseley Hill that movements of the trap have also affected, as before stated, 

 the carboniferous strata, which there repose unconformably upon the edges of the older rocks. Pro- 

 ceeding to the E.N.E. in the direction of the axis, there are about five miles of country in which no 

 rocks are visible, the valley in which the Severn flows being thickly covered with gravel and other de- 

 tritus ; but in the environs of Ness Cliff, hills of New Red Sandstone rise from the plain and are 

 more or less continuous for many miles to the E.N.E., precisely in the prolongation of the axis of the 

 Breiddens. 



The axis of the Moehy-Golfa ridge is well exposed in a small hill, six miles and three quarters 

 west of Shrewsbury, recently cut through in lowering the Holyhead road, where strata of dark red, 

 yellowish, and whitish red, thin-bedded sandstones are tilted 35° to the N.N.W. or at right angles 

 to the axis. The vast accumulations of detritus of New Red Sandstone, mixed up with fragments 

 of trap, Cambrian, Silurian, coal measure, and other rocks, which are piled up in Ensdon Hill and 

 other localities between this line of elevation and the town of Shrewsbury, are thrown off upon the 

 southern flank of the eruptive line. Following this line we find it preserving the true character 

 of an anticlinal, for in the hills around Great and Little Ness, the strata of sandstone rise to the 

 surface in dome- like forms, and after passing over a denuded tract covered with enormous accumu- 

 lations of gravel, clay, and boulders 2 , an unequivocal anticlinal is exhibited in Pim Hill, where the 

 sandstone emerges from the plain and rises to a height of about 600 feet. On the northern slopes 

 of this hill, thick beds of yellowish friable sandstone dip 25° N.N.W., whilst on the southern, or 

 towards Shrewsbury, beds of deep red sandstone incline to the S.S.E. 



But it is not merely the reversed dip which indicates the direction of the axis of elevation, for 

 the sandstone in the central portion of the hill is so hard, white, and compact, and in so unstratified 

 or amorphous a condition, that it has every appearance of having undergone great alteration. It is 

 made up of fine grains of quartz, cemented by decomposed felspar, and though not altered to the 

 same extent as the sandstones of the Silurian System which I have shown in previous chapters to 

 have been changed into granular quartz rock, there is a close approach towards that state. This 

 amorphous mass having been cut into for the use of the roads to the depth of forty feet, is rent by 

 vertical fissures, the faces of which are frequently in the state of slickenside. Crystallized carbonate 

 of lime is detected in small veins, and earthy oxide of manganese is both disseminated in grains 

 through the mass and spread in thin films over the faces of the fissures. Stratification is perceptible 

 only towards the sides of the quarry and near the summit, where the beds recovering their ordinary 

 friable structure, dip to the N.N.W. and S.S.E. The whole in fact constitutes one great quartzose 

 veinstone, running transverse to the strike of the beds, whilst numerous minor veins of similar com- 

 position cut across the strata in the adjoining slopes. 



1 In the second visit to establish this point I was accompanied by Mr. W. Hamilton, Sec. G.S. 



2 See account of these boulders and gravel in the concluding chapters. 



