238 Reports and Proceedings — Geological Society of London. 



but north and south of Tintagel Head the higher members appear, 

 greatly faulted, being brought in out of their true position partly 

 by a change of strike, partly by dip-faults. The most distinctive 

 rocks, utilized as a datum for mapping, are a group of ashes and 

 lavas. The latter are often amygdaloidal, and possess original 

 characters which are still recognizable ; but the whole group is 

 frequently much altered or entirely reconstructed, with the formation 

 of epidote (sometimes enclosing allanite), sphene, biotite, chlorite, 

 etc. The rocks are associated in many instances with calcite, at 

 least partly due to contemporaneous deposition, but frequently 

 forming a corporate part of the renovated rock, and the mineral 

 is found with quartz and translucent felspar. 



Bluish-black slates and finally laminated quartzose beds overlie 

 and underlie this volcanic series. 



The remaining rocks are phyllites, closely resembling those from 

 the Ardennes. The author divides them into four groups. The 

 highest of these (Tredorn Beds) overlies the uppermost division 

 of the Blue-Black slates, and in the western part of the district 

 contains a mineral forming small white spots, not yet determined. 

 The beds underlying the Lower Blue-Black slates (Halwell Cottage 

 Beds) are banded phyllites, with quartzose laminae, typically con- 

 taining abundant crystals of clinochlore with a habit resembling 

 that of ottrelite. The underlying phyllites (Penpethy Beds and 

 Slaughterbridge Beds) contain no distinctive mineral. Taken as 

 a whole, the phyllites consist of a sericitic and chloritic groundmass 

 containing unorientated crystals of white mica, micaceous ilmenite, 

 ha9matite, and minor quantities of tourmaline and rutile. North- 

 east of Camelford (Grigg's Down) they furnish clear evidence of 

 contact-metamorphism. 



III. — April 8th, 1903. — J. J. H. Teall, Esq., M.A., F.E.S., 

 Vice-President, in the Chair. 



Professor W. W. Watts drew attention to the exhibit on the table 

 of the new series of Platinotype Photographs issued by the Geological 

 Photographs Committee of the British Association. 



The following communications were read : — 



1. " On the Probable Source of some of the Pebbles of the Triassic 

 Pebble-Beds of South Devon and of the Midland Counties." By 

 Octavius Albert Shrubsole, Esq., F.G.S. 



After an account of previous researches on this subject, the author 

 proceeds to describe the Budleigh Salterton Pebble-Beds. Judging 

 from lithological evidence, the bulk of the pebbles must have come 

 from a definite region of a comparatively simple geological character ; 

 and this is confirmed by the palceontological evidence. The sup- 

 position is natural that Devonian rocks were once represented 

 either in the Calvados district or in some region in the same 

 drainage area as that which has supplied the Ordovician element. 

 The Gres de May of Normandy and its associated rocks are next 

 described, a massif which, according to Professor Bonney, must 

 have exceeded the Alps in breadth. When regard is had to the 

 extent and original thickness of the Gres de May, it appears capable 



