CARADOC FORMATION IN MOEL-Y-GARTH, GAERFAWR, ETC. 305 



Separated from the zone of Welch Pool by the flags and mudstone of the intervening ridge of 

 Golfa and its dependencies, is another low elevation of red rock near the Quakers' burial ground. 

 It is composed of slightly micaceous and argillaceous red sandstone, overlaid by slightly calcareous 

 beds and quartzose red conglomerate, fine-grained purple grit, and flag-like sandstone, containing 

 portions of trilobites {Trinucleus) and rounded impressions of stems of encrinites, precisely like 

 those of the Caradoc sandstone. The pebbles are quartz, varying in size from hens' eggs to beans, 

 and the matrix is calcareous; the beds being separated by thin courses of red spotted shale and 

 calcareous concretions of red, green and purple colours. These beds dip 45° to the N.N.W. and 

 are traversed by a number of joints. The line of this elevation of the lower rocks is indistinctly 

 traceable to the north-east into the high road between Garth and Welch Pool. It is met abruptly 

 by a much higher elevation of similar rock in the hill of Moel-y-Garth (860 feet above the sea), the 

 direction of which is transverse to that of all the ridges of this district, being nearly north-west of 

 south-east 1 . The structure of this remarkable hill is well exposed in different quarries on its south- 

 western face, where the beds dip away to the W.S.W. at angles varying from 40° to 60° and consist 

 of flaggy, grey sandstone and shale, hard, purple conglomerate grit and sandstone, greenish and 

 brownish, slightly micaceous, grey sandstone, &c. In these beds are casts of the large Orthis 

 expansa, PI. 20. f. 14, and other shells, with encrinital stems. The rocks of the Moel-y-Garth have 

 a tendency to slaty cleavage, the laminae in one part being nearly vertical, and ranging from 10° east 

 of south to 10° west of north. In quarries near the summit of the hill the brownish hard sandstone 

 is split by joints into parallelopipeds, the surface of the beds being covered with black and purplish 

 blue oxide of iron and some thin pellicles of shale. Beyond the north-western extremity of Moel- 

 y-Garth, the strata resume the prevailing strike of the country, and red rocks of the Caradoc sand- 

 stone, occupying hillocks at Hendrechen, range to the north-east by Croes-wood to Gaerfawr, where 

 they attain the height of 754 feet. 



Gaerfawr 3 , though of no great altitude, is a very striking object, for as it is the last hill of any 

 note upon this parallel, it impends over the flat valley of the Severn. An excellent transverse section 

 of a portion of the Caradoc sandstone is seen in a gorge passing from the valley of Guilsfield to the 

 north-west of Gaerfawr. The strata dip to the west and north-west, at angles which are highest 

 near Guilsfield and decrease in the overlying strata, which succeed each other in the following 

 ascending order : 



1. Argillaceous, sandy shale. 2. Thin-bedded, highly micaceous, hard sandstone, splitting into rhombic fragments, with 

 casts of shells on the surfaces of the beds. 3. The same sandstone with casts of shells marked by yellow hydrate of iron ; 

 beds four inches to one foot. 4. Thick beds of calcareous grit, passing upwards into a light grey impure limestone with 

 fossils : forty or fifty feet of this rock are exposed in one quarry, the beds dipping from 40° to 35° to the north-west, but 

 only the three or four feet of the uppermost stratum are calcareous. 5. Grey shelly sandstones form the western and 

 north-western slopes of the Gaerfawr, with some courses of sandy shale and two bands, at least, of dark indigo, subcrystal- 

 line limestone. 



1 LordClive informed me that owing to this transverse direction Moel-y-Garth is called in Welch the Head- 

 land of Powis, being in fact laid athwart the other ridges. (See Map.) 



2 Impure limestone, forming part of the Caradoc formation and similar to the rock of Gaerfawr, is well laid 

 open in quarries at the north-western foot of Moel-y-Garth, where in my last visit (Oct. 1836) I observed 

 several convoluted fossil forms with which I was not familiar, but was unprovided with a sufficiently heavy 

 hammer to extract them. I recommend this quarry to the attention of the fossilist ; it lies about one mile 

 south and by west of Guilsfield. 



