METAMORPHIC ROCKS OF SOUTH DEVON. 



727 



slight evidence which would rather connect it with the effects of 

 pressure. One example, which had some weight with me, was a 

 case of chlorite-schist interbanded with a 15-inch mica-band. The 

 mica-schist showed puckerings, which I can best describe as giving 

 an outline roughly duplico-dentate, and the transverse planes of the 

 chlorite ran up into the sharp teeth of the puckerings. It seemed 

 as if the force which crumpled the mica-band had developed the 

 oblique planes in the chlorite. At other localities also, the divisions 

 seemed to be suggestive of pressure-planes, as in exposures near 

 Rickham Signal-station, on the shore east of Portlemouth Parsonage 

 and elsewhere. For comparison with these examples I searched 

 on the shore south of Portlemouth for an occurrence in chlorite- 

 schist, referred to by Professor Bonney *, and described as a cleav- 

 age-structure, and I think the cases I have quoted will bear a 

 similar explanation. To such pressure-planes crossing those of 

 bedding, modified by the not very plastic material of the rock 

 in which they are developed, I am inclined to attribute the 

 irregularly worn surfaces of the chlorite-schist ; since the hollows 

 which weather out at places can be found in all gradations from 

 regular angular rhombus-shapes to rounded and irregular pits. The 

 rounded depressions, like the angular ones already described, follow 

 planes of bedding ; in one example I traced them along the con- 

 tortions of a corrugated mass of chlorite-schist. Where the pitting 

 was most irregular in its arrangement, the beds had often suffered 

 such foldings and dislocations that it was difficult, or even impos- 

 sible, to track the bedding-planes. 



The angular markings I have alluded to were generally rather 

 local in their occurrence ; but over large masses of chlorite-schist 

 there was a development of a second set of planes, presumably 

 joint planes, along which the rock continually broke up and slipped. 

 This often gave erroneous impressions as to the dip of beds seen 

 from a distance. 



III. Stratigraphical Relations oe some oe the Metamorphic 



Bocks. 



In this part of the paper I shall restrict myself mainly to the 

 small northern area beyond Portlemouth, which was not specially 

 examined by Professor Eonney. The best exposures are along the 

 main Salcombe estuary, whose shores, extending roughly from north 

 to south, cut across successive beds. The eastern cliff is perhaps 

 rather less disturbed, and from it chiefly we may describe a typical 

 succession. 



1. (a) Interbanded Series of Main Estuary and Batson. — South 

 of the fault, near Halwell Wood, we come to a mass of mica-schist, 

 partly brown from decomposition, which dips northerly and extends 

 about 100 yards ; beyond this, chlorite-schist is exposed. Hence, 

 nearly to the beginning o£ " Scoble Point," we have beds, at first 

 and at places, with variable or southerly dip, but, on the whole, 



* Quart. Journ. Geol. Soc. 1884, vol. xL p. 9. 



