TRAP AND ALTERED CAMBRIAN ROCKS — LONGMYND, ETC. 259 



Shrewsbury road. The dark-coloured schist around this boss of green-stone, and particularly as 

 seen on the sides of the high road, is in an indurated and brittle slate, and breaks into small shivery 

 fragments, with glossy surfaces having a purple plum colour. These altered and vertical strata ex - 

 tend to Church Stretton, where the protrusion of the trap rock and the hardening and fracturing of 

 the schist in contact, are remarkably well displayed at several points ; an excellent example oc- 

 curring near the spot called the World's End, opposite the principal inn. 



The greenstone is hard, sometimes compact, sometimes crystalline, and is traversed by veins 

 of carbonate of lime. It rises in round knolls through the schistose beds, upon which it has 

 produced powerful effects ; the lamination being obliterated, and many of the thin layers cemented 

 into a mass of so indurated and compact a nature, as to resemble flinty slate. It is also traversed 

 by veins of white quartz and carbonate of lime. This altered mass splits into trapezoidal and cubical 

 forms, of which it is almost impossible to obtain a cross fracture. At twenty or thirty paces from 

 the trap, the schist, though violently contorted, has in some degree recovered its lamination, and 

 upon fracture the rock peels off in layers under the hammer ; but we must recede some hundred 

 paces from the intruding rock before the beds entirely recover their natural depositary characters 

 and become the ordinary dark gray schists or clay slate. The whole of the mass of schist around 

 the grounds of the Rectory is more or less altered, and two or three other knolls of crystalline green- 

 stone rise to the surface. In this greenstone are many crystals of iron pyrites. At Brockhurst 

 Castle to the south of Stretton, a thin dyke or course of greenstone has given to that wooded knoll its 

 picturesque form, and the beautifully varied outline of hill and dale in this romantic spot is due to 

 the same cause, the trap rocks and the associated indurated beds of depositary origin occupying the 

 summits, whilst the soft and decomposing shale and schist have been worn into deep dingles. 



The Longmynd, as before stated, lies to the west of the Stretton Valley, and is watered by 

 several brooks, which descend in the deep " gutters running from north-west to south-east, and 

 offer transverse sections of all the rocks of which the Longmynd is composed. Two of these merit 

 description, as they develop the structure of the mountain. 1st, The brook which flows to Church 

 Stretton, 2nd, That which waters Little Stretton. 



In ascending the former, and entering the region of hard grey and greenish-grey sandstone, 

 we meet with some protuberances of trap, followed by highly altered hard white and green 

 beds, either in vertical positions, or dipping 80° north-west. The trap can be detected at 

 two points. At the first, it is a pinkish amygdaloid, containing kernels of green earth in a base 

 of compact felspar. This is visible only in the bed of the brook, where the bedding of the 

 contiguous slates is entirely obliterated. At the second the trap, close to the amygdaloid, is 

 a dark- coloured, crystalline greenstone. The dislocation of the strata at this spot (above the 

 carding-mill), is very striking, and the rocks have much the character of true slates, being 

 very similar to some of the light green slates on the flanks of Snowdon. The ordinary composition 

 of the slaty sandstone and conglomerate of this mountain has been previously detailed, and I allude 

 to the old slaty aspect of the beds only, because it is principally displayed at points near which the 

 trap rock protrudes. 



The defile which traverses the Longmynd from near the summit (where the trigonometrical pole 

 was fixed) to the village of Little Stretton, is, however, by far the most instructive of these 

 natural sections. In this descent, of about two miles, I enumerated upwards of twenty pro- 

 tuberant heads of trap. Some of them are bosses of considerable size ; others, mere heads of 

 larger dykes, which rise for a few feet or yards above the stream, and are dovetailed, as it were, 



