408 PROCEEDIIs^GS OP THE GEOLOGICAL SOCIETY. [April 22, 



The volcanic rocks on the north of Dunterton and Quether pass 

 Tinder a belt of dark slates and chert, which ranges up from Lan- 

 diie, south of Launceston, by Greston Bridge to Staddon, and thence 

 to Littonary Down, where, thrown to the south-eastward by the 

 fault already mentioned, it is continued by Bowdon Down to East 

 Longstone ; and this in turn passes under the higher band of volcanic 

 rocks of Bradstone, Chillaton, and West Longstone, It is this chert 

 and its associated grit and slate which constitute the higher beds 

 of Heathfield Down, on the west of the Brent Tor faults. 



Still higher beds, consisting of dark-blue and greenish-grey slates, 

 with seams of grit and nodules of ironstone, range up from the 

 Tamer north of Bradstone, by Kelly and Marystow, and along 

 the valley of the Lyd river to the Lydford railway- station, and 

 thence pursue a north-easterly direction by Lydford and Down- 

 town to the granite. These slates are finely exposed in the railway- 

 sections between the Lidford and the Coryton stations. They are 

 evenly laminated, dip northerly, and rest upon the volcanic rocks 

 of Chillaton and West Longstone. The volcanic rock of Medwell 

 appears to be the same as those of Bradstone and Chillaton, cropping 

 out on the north side of a narrow synclinal fold which extends from 

 Kelly to Green Cross, while the chert of Lawhitton, Hardow Down, 

 and Kelland is the underlying rock of Staddon and Littonary Down 

 again brought up to the surface, separated from the chert of Gordon 

 Hill by the northern continuation of the Lyd-river slates, which 

 range by Trenefell to the north of Tremale, where they are worked 

 for roofing-purposes. 



On the north of this belt of slaty rocks are the small lenticular 

 deposits of dark-blue or black limestone of Cury Park, Poleat Corner, 

 and Coryton Eailway-station ; and beyond these there is a range of 

 chert-beds, which constitutes an important feature in the country, 

 and forms a ridge of barren land which is easily followed. This 

 chert forms the high ground of Gordon Hill, east of Launceston, 

 where it is underlain on the north by black slate and the lime- 

 stone south of Timber Bridge, and is continued east of the Tamer, 

 by Sydenham and Leigh Down, to the Lew Water. It includes the 

 volcanic ash-beds of Whitley and Leigh Down, and is exposed in 

 quarries by the side of the railway west of Sydenham. A. second 

 patch of chert, which, although on nearly the same line of strike, 

 appears to be disconnected from the last, is seen immediately to 

 the north of the limestones of Poleat and Cury (some slates, how- 

 ever, intervening), and is continued on the north side of the road 

 to Watergate, through Burley Down, to a farm marked Buddie 

 Brook on the Ordnance Map. This chert occurs for the most part 

 in rather thin beds ; but they are contorted and crumpled to such an 

 extent that the beds are often folded completely back upon them- 

 selves, and in looking at them it is impossible to avoid the conclu- 

 sion that the more argillaceous slaty rocks cannot have escaped the 

 influence of the forces which have contorted these harder rocks in so 

 remarkable a manner, although it is not equally apparent in them. 

 Slaty rocks lie to the north of the chert-beds similar to those on 



