Cornwall and South Devon. 343 



limestones in their absence. My arrangement, in fact, of the 

 South Devon limestones has been governed entirely by the 

 order and succession of the killas and carbonaceous series 

 which there severally envelope them, and there is no other 

 rule, with security from error, which can be relied upon : the 

 slates and grits are constants, — the limestones accidents: in 

 this view the lime-rocks of Buckfastleigh, Ashburton, Bicking- 

 ton, Chudleigh, Ideford and Lyndridge, belong to the flori- 

 ferous or carbonaceous series, at about the same level as the 

 Bampton, Holcomb-Rogus, and Westleigh limestones on the 

 north, — all of them perhaps not much below the horizontal 

 parallel of the Petherwin. Some of the Chudleigh fossils, so 

 far as their evidence is of any value, are apparently identical 

 with some of the Petherwin. 



It appears throughout to be as poor in metals as No. 4, as 

 I do not remember any lode of any promise or importance 

 being worked in it : it however affords roofing-slates which I 

 believe would equal in quality any in England, if quarried to 

 a sufficient depth, and with the requisite skill and capital. 



Its northern line or boundary ranges from Staple hill on 

 the south-west of Bovey heath near Chudleigh, by the north 

 of Ingsdon, to a little south of Bickington and Ashburton ; a 

 little east of Buckfastleigh ; the south of Dean church ; South 

 Brent, and Ivybridge, to Beechwood and Sbaughwood, up to 

 which point it is in hard junction with the carbonaceous rocks : 

 from thence it takes a westward strike (accompanied by the 

 Tintagel killas No. 1, which there first sets on) to Tamerton 

 Foliot ; the north of Landulph ; Pillaton, and the north of 

 Quethiock, to the south foot of Caradon down : from hence 

 the entire series is represented chiefly by a narrow band of 

 the upper beds which flank the granite, by St. Neots to Car- 

 dinham, on the west of which it again expands, and ranges 

 after the west escarpment of the granite to Blisland and the 

 west of St. Breward, where meeting again with the lower 

 killas series No. 1 (which had described a great semicircle 

 from St. Ives round the same Bodmin Moor granite by its 

 eastern, northern, and north-western frontiers), they range 

 together in a nearly east and west direction by a little north 

 of Endellion, to the sea, between Portquin and Porteath : 

 strange as these remarkable lines may appear to some, I am 

 convinced they will be obvious to any one who will follow 

 them out as I have done. 



Its southern terms are clearly deflected to the north-west, 

 on the west side of the Tamar, conformably to the deviation 

 in strike of No. 3 at Cawsand, as before adverted to : ad- 

 vancing in this direction towards Menheniot and Quethiock, 



