TRAP IN NEW RED SANDSTONE PROCEEDING FROM THE BREIDDENS. 295 



have further shown that this contemporaneous class has been afterwards broken through 

 and dislocated by intrusive trap, and special attention is now invited to dykes which, 

 proceeding from the Silurian System, affects also the New Red Sandstone of Shrop- 

 shire. In concluding this chapter, therefore, I will describe: 1st. The trap dykes 

 alluded to. 2ndly. The connection of these dykes with a distant mountain mass of 

 trap rock. 3rdly. The signs of elevation and alteration perceptible in the New Red 

 Sandstone along axes coincident with the direction of these intrusive rocks. And 

 4thly. It will be shown that this line of elevation serves to explain how the great out- 

 lier of Salopian Lias was dissevered from the chief mass of that formation. 



In the summer of 1834, the mansion of Sir Andrew Corbet, Bart., at Acton Reynolds, eight miles 

 north of Shrewsbury, having been subjected to a thorough repair, the ground beneath and around it 

 was cleared to the foundations, when masses of a hard, dark rock were discovered, passing like walls 

 through the sandstone upon which the house is built. Being informed of this circumstance 1 , I 

 visited the spot ; and although at that period a great portion was covered up, sufficient was exposed 

 to explain the nature and relations of these rocks. The part which I inspected was a dyke about 

 four feet and a half wide, chiefly made up of concretions, which cut through the horizontal beds of 

 sandstone from north-west to south-west. The sides of the trap were vertical, and between them and 

 the sandstone was a thin " sahlband " or coating of decomposed felspar. The contiguous sandstone 

 was indurated for a few inches, and contained disseminated grains of earthy oxide of manganese, 

 but at a greater distance it had its ordinary characters. These strata belong to the central mass of 

 the New Red Sandstone, and immediately underlie the stone of the celebrated quarries of Grins-hill, 

 distant about one mile, (see pp. 39 et seq.) In its course to the south-east, this dyke in passing 

 under the house expands to a width of eight or nine feet, and therefore the portion which I examined 

 was possibly near its termination. A second dyke, parallel to the above, ranges beneath the western 

 part of the house. A third and larger dyke trends from E.N.E. to W.S.W. and consequently cuts 

 across the two parallel dykes. The point of intersection of this transverse dyke with that first 

 described having been covered by the progress of the building, I was prevented from personally 

 examining it; but I collected specimens which had been extracted, and as they precisely resemble 

 the rock I saw, there can be no doubt that the small dykes running from south- east to north-west 

 were mere branches from the large central dyke. The rock consists of two varieties : 1st. A por- 

 phyritic greenstone, consisting of a dark-coloured base of hornblende and granular felspar with white 

 crystals of common felspar. 2ndly. A mottled, rough concretionary rock, made up of pink and dark 

 grey compact felspar with imbedded crystals of common felspar, the concretions often assuming 

 angular forms and thus resembling a breccia, but as they and the matrix are of similar composition 

 the whole must be regarded as concretionary. As I was well acquainted with both these varieties of 

 trap, having previously examined them near Welch Pool and in the Moel-y-Golfa range of the Breidden 

 Hills, and as I perceived the direction of the principal dyke would if prolonged, terminate precisely 

 in that range, it occurred to me that, although Acton Reynolds was fifteen miles distant from the 

 Breiddens, these dykes might be connected with that great centre of igneous eruption. I was fur- 

 ther disposed to adopt this view, upon observing that the chain of hills of New Red Sandstone which 

 extended over the intermediate country offered evidences of dislocation. Further inquiry confirmed 



1 By Mr. Carline, the architect. 



2 o 2 



