394 TROF. J. F. BLAKE ON THE MONIAX AXD 



towards the west, we pass from irregular grits of the older series to 

 purple grits with fragments of slate, theuce to well-bedded vertical 

 pale slates, exactly like those of No. 5, and then on the descending 

 slope of the hill to the grit with slate fragments again. As far as 

 this spot would show, there might therefore be an interbedding, but 

 evidence elsewhere necessitates another reading which is indicated 

 by the curve on the map. 



A little to the south of this the line of junction becomes very 

 nearly parallel to the Portway, along which for a couple of miles 

 there are occasional exposures of the purple grits and fine conglo- 

 merates. If this line were continued northward, it would nearly 

 coincide with the eastern boundary of the patch of purple grit south, 

 of Woolstaston, — a fact which certainly suggests that the great area 

 of purple slates and greywackes now exposed to the west of this 

 patch has been laid bare by the denudation of a superficial continu- 

 ation of the purple grit. 



On and near the roads into which the Burway branches on reach- 

 ing the hill-summit, are seen other exposures requiring explanation. 

 On the western slope of a small depression at the bend of the north- 

 ern road is seen a crag of purple slates and greywackes, with the 

 usual high dip and ordinary strike, but on the eastern slope of the 

 same depression is a mass of unbedded conglomerate, seen in several 

 crags on about the same level, and this is followed by coarse purple 

 grit, till the line of the regular junction is reached ^ of a mile to the 

 east. What happens to this patch of slate and greywacke to the 

 north is not seen, but it is cut out by purple grit on the south, and 

 reappears a little further on in surface-exposures over a limited 

 area. The great regularity of the slates and greywacke's, and their 

 numerous alternations in the crag, forbid the idea of a local deposit in 

 the midst of the conglomerates and grits. The very limited develop- 

 ment and absolute absence of any indication negative the notion of a 

 fold ; but all of this combined with the fact that the relations are 

 not here with the basal grits, but with the higher conglomerates, 

 point to an unconformity and an irregular surface, in other words 

 that these two patches of the older slates are ordinary inliers. 



About I of a mile to the south of these inliers, we have the con- 

 verse phenomenon to deal with, — the conglomerate and grit form a 

 well-marked outlier (see fig. 2). The northern end of this is seen 

 in Ashes Hollow, along the south-western slope of which it forms 

 near jS'arnells rock, which is also composed of purple grit, a horizontal 

 crag. Now if we work along the valley-bottom of the Ashes Hollow, 

 and examine only the rocks which are abundantly exposed all along 

 the stream and pathway side, we shall emerge on the Portway, by 

 Pole Cottage, without seeing anything else than purple-weathering 

 pale slates and greywackes, or having any notion aff'ordcd of the 

 presence of massive purple grits or conglomerates. It is only when 

 we climb to the crag which overhangs the southern slope, and which 

 has an unusual appearance even at a distance, that we find these grits, 

 so far away from where we should expect them. On the northern 

 slopes there are numerous exposures of rock, but not one of them is of 



