142 PROF. T. T. GROOM ON THE GEOLOGICAL [Feb. I90O, 



that all these instances occur close to the western boundary of the 

 Archaean massif, and that the foliation appears to show a definite 

 relation to the direction of this boundary. 



The behaviour of the Silurian rocks on the west of this boundary 

 is interesting. As already pointed out (p. 139), the May Hill Sand- 

 stone of the ' Silurian Pass ' dips north-eastward : that is, directly 

 towards the Archaean mass of Hangman's Hill. Near Warm's Well 

 the Silurian rocks exhibit a tendency to curve round, and to con- 

 form to the outline of the Beacon ; that they are inverted is shown 

 by the Woolhope Limestone, which, as observed by Phillips, dips 

 eastward at 40 . 1 Farther north-west the Malvernian rocks 

 are in contact with the Wenlock Shale ; this is exposed in a 

 stream west of Wind's Point, where it shows an inverted dip of 

 about 30°. The Woolhope Limestone may be obscurely traced by 

 debris from a point south-east of this in a north-easterly direction ; 

 the May Hill Sandstone also sets in again close to Wind's Point, 

 but can be traced by debris only. As on the southern side of the 

 Beacon, the Silurian strata tend to conform to the outline of the 

 Archaean mass. These relations are seen in the accompanying map 

 (PI. VIII), which agrees closely with that published by Phillips and 

 by the Geological Survey. 



The Wenlock Limestone, forming the peculiar curve west of 

 Walm's Well mapped by Holl, 2 may be traced in a general 

 northerly direction for the whole length of the Herefordshire 

 Beacon. All nlong the line it has an inverted dip. It is apparently 

 reduced in thickness towards the middle of this part of its course. 

 On the west maybe seen the Lower Ludlow Shales, exposed at 

 the entrance-lodge of Eastnor Park, where they are about vertical ; 

 in the main road, a little to the north-west, they have an inverted 

 dip of 63°. A fine exposure is seen down a lane leading from the 

 east towards Oldcastle Farm, where the shales have an inverted 

 dip varying between 50 c and 58°. 



The Aymestry Limestone appears to be cut out by a fault in 

 the neighbourhood of Oldcastle Farm. This runs along a marked 

 depression separating the normally dipping Aymestry Limestone 

 and Ludlow Beds south of Oldcastle Farm from the inverted Lower 

 Ludlow Shales on the east. 



The curving round of the Silurian strata, the inverted dips, and 

 the disappearance of the May Hill Sandstone, Woolhope Limestone, 

 and part of the Wenlock Shale may be best explained, I think, on 

 the supposition of overfolding culminating in the overthrust of the 

 Malvernian Series on to the Silurians. The actual junction, it is 

 true, is nowhere exposed, but its course across the contour-lines 

 from Walm's Well to Wind's Point, which can be fixed within 

 narrow limits, agrees with the supposition that one is dealing here 

 with a plane-fault, or thrust-plane, having a low easterly dip. (See 

 figs. 2 & 3, p. 141.)- 



The tendency of the Archaean rocks to show a schistosity with 



1 Mem. Geo!. Surv. vol. ii (1848) pt. i, p. 71. 



2 Quart. Journ. Geol. Soc. vol. xxi (1865) p. 73. 



