1868.] HOLL SOUTH DEVON AND EAST COKNWALL. 439 



wards of 20,000 feet for the relatively small portion of the South- 

 Devon series which overiies the Torbay limestones, — an estimate 

 which would be beyond all probability. 



This higher group of rocks is only very sparingly fossiliferous. A 

 few fossils are stated to have been found in the cliffs of Plymouth 

 Sound ; and Encrinites occur in the calcareous seams at Kingswear. 

 Mr. Pengelly has seen traces of them in Scabbacombe Bay and at 

 Beeson Cellers, near Torr Cross ; but these remains are in such a 

 wretched condition that, with the exception of Petraia Celtica, 

 Lonsd., I am not aware that any of them have been determined. 



IV. Metamorphic Rocks of the Salcombe district. 



These rocks consist chiefly of mica- slate and of a mixture of gra- 

 nular quartz with a mineral allied to chlorite, and have been fully 

 described by the late Sir Henry de la Beche in his ' Report of the 

 Geology of Devon and Cornwall ' *, and by the authors of the ' De- 

 vonian System,' in the memoir already quoted f, to which reference 

 must be made for mineral details. As observed by the latter au- 

 thors, mica-slate prevails most towards the south, and the chloritic 

 rocks towards the north ; but the different varieties are so com- 

 mingled that they cannot be separated into two formations J. Al- 

 though greatly undulated and contorted, they have a general dip 

 towards the argillaceous-slate system on the north, which has like- 

 wise a northern dip ; but the actual contact is nowhere seen, and the 

 manner in which the altered and unaltered rocks are brought into 

 apposition is somewhat obscure. The argillaceous rocks are high up 

 in the Devonian system ; nevertheless no clear evidence of a line of 

 fault between them and the metamorphic rocks has been observed. 

 Assuming that the latter belong to some earlier epoch, it is possible, 

 perhaps, that they may have been thrust up from below, break- 

 ing !^hrough all the lower beds of the Devonian series, while they 

 carried up and threw off to the northward the higher beds of the 

 Kingsbridge district. Such an hypothesis is quite consistent with 

 what we know of the general relations of the slaty rocks of South 

 Devon, and may assist in explaining the relative positions of the 

 beds, as the metamorphic rocks might then have formed a counter- 

 force to that Avhich brought up the granite of Dartmoor, and have 

 contributed to the production of those long narrow anticlinal and 

 synclinal folds into which the intervening slaty rocks have been 

 thrown. At the same time, it must be observed, these altered rocks 

 of Start Point and the Bolt have not a very ancient aspect, and the 

 dark -blue slates of Hopes Cove exhibit that minute crumpling and 

 abundant intersection with veins of red and white quartz so fre- 

 quently observed in slate rocks at the point of commencing metamor- 

 phism. Moreover the rocks appear on the whole to be more highly 

 crystalline, and the effects of metamorphic action seem to increase 

 progressively, as we proceed towards the south ; and it appears to 

 me more probable that these micaceous and chloritic rocks are 

 altered depositions of Devonian age, mantling over a granitic mass, 



* P. 27. t Pp. 658 and 661. \ L. c. p. 659. 



