444 PROCEEDINGS OF THE GEOLOGICAL SCCIETT. [April 22, 



red rocks of Staddon Point, Morleigh Down, and the Dart river 

 have been brought up from below the Plymouth limestone by an 

 inverted anticlinal axis ; and I believe Mr. Beete Jukes is inclined 

 to favour this view. There appears to be, however, on the east 

 shore of Plymouth Sound, south of Mount Batten, and from the 

 limestone of Brixham, along the river Dart, and the coast at Mann 

 Sands, an upwards series, through grey, blue, and purple slate, to 

 the red grit, which rocks succeed each other conformably ; and the 

 limestone of Berry Pomeroy and Marldon are overlain by variegated 

 argillaceous slates, surmounted at Blagdon Cross by red grits Kke 

 those of Staddon Point and the banks of the Dart. No similar rocks, 

 however, are seen rising up from below the limestone among the 

 lower rocks north-west of Dartington and Ogwell ; nor are any such 

 again brought up to the surface from beneath the limestone in the 

 long downward succession of the beds between Plymouth and the 

 Harrowbridge station, on the Tavistock railway. 



The fossiliferous rocks of South Petherwin appear to be commonly 

 held among geologists to be Upper Devonian, and are placed by 

 Mr. Salter on the horizon of the red slates of Morte Bay *. Look- 

 ing, however, to the relations of the beds which surround the granite 

 of the Camelford Hills, and following, as I have done, the volcanic 

 rocks of Alternan and Lewannick, which support the Petherwin 

 limestones, round to the westward by St. Clether, Davidstow, and 

 Tintagell, to Delabole and St. Mabyn on the one hand, and by 

 Stoke Climsland, South Hill, Calhngton, and New Bridge, to St. 

 Cleer and the vicinity of Liskeard on the other, there seems to be 

 no reasonable doubt that we are following the same range of 

 beds, and that the granite, in breaking through and carrying up the 

 Devonian rocks, has done so without producing so great an amount 

 of disturbance as to destroy the general relations of the surrounding 

 rocks, although some lower beds are brought up on the south-east 

 and north-west of the granitic mass, and carry these volcanic 

 rocks further from its margin. There appears, therefore, to be 

 evidence, as clear as we can expect to find among rocks of this 

 kind, that the igneous rocks which are seen to dip away from 

 the granite on all sides except that towards Bodmin, all belong to 

 a single group ; and that the band of volcanic rocks at Alternan, on 

 the north, holds the same relative position as regards the granite 

 that the smaller, but similar, band at St. Cleer does on the south- — 

 in other words, that the igneous rocks of .ilternan and St. Cleer, 

 and the more horizontal masses further to the east at South Hill 

 and Callington, are on the same, or nearly the same, geological ho- 

 rizon. Now we have a tolerably clear upward succession from 

 the beds which are thrown over to the north of the Hingston Down 

 granite, and which range up to Alternan, across the strike to 

 the limestones of South Petherwin — and an equally clear downward 

 series from Whitechurch Do-rti, along the Tavistock railway, to 

 Plymouth. If, therefore, the Petherwin limestones were really 



* "Upper Old Red Sandstone and Upper Devonian Rocks," Quart. Joum, 

 Geol. Soc. vol. xix. p. 484, ISfiS. 



