1868.] noLL — souTU devon and east Cornwall. 421 



To the c<ast of the fiuilt which passes Lostwithiel, tiiid wliich is 

 probably continuous with the Tywardreath copper-lode, the country 

 is upraised, and the rocks are similar to those of St. Breock's Down, 

 much traversed with quartz veins, blocks and fragments of which 

 lie about in abundance. The gritty and arenaceous beds form a 

 narrow belt of country, which extends from the north of Black Pool 

 by the Grey Mare and liye Down, and between Boconnock and 

 Broadoak, to Bucka-Barrows and Bury Down ; and the grit beds 

 south of St. Keyne appear to be the continuation eastward of the 

 same belt of rocks. Opposite the Parsonage at St. Keyne these grits 

 lie horizontally, and there can be no doubt about their passing under 

 the argillaceous and calcareous rocks on the south ; but it is not so 

 clear whether they rise from under the slaty rocks on the north at 

 St. Keyne, or whether they are faulted against them. These grits, 

 with the thick slates which overlie them, together with those which 

 form the high ground between the forks of the Towey Biver at St. 

 "Winnow, and the south-east of Lostwithiel, constitute a somewhat 

 triangular area, having the Lostwithiel fault at its base, which 

 separates and dovetails in between the higher rocks of the Liskeard 

 synclinal trough as it crosses the tributaries of the Powey, south of 

 Warleggon, and St. Neots on the north, and the rocks of similar age 

 as they strike from the Looe river below Tredinick by Lanreath 

 and St. Veep to Trewardreath on the south. In this view, I am 

 compelled to differ from the opinion of the late Sir Henry De la 

 Beche, who held that the thick slates and grit beds of Boconnock 

 and Bye Down are higher beds overlying the red slates of Lansalloes 

 and Gregon* . The reasons against this will become more apparent 

 when we have followed up the higher rocks from the eastward. 



To return to the beds which skirt the Camelford granite on 

 the north-west. The volcanic rocks of Alternan and North Hill 

 terminate near Kelbrook, being broken through by an elvan ; 

 the similar rocks of Bray's Shop, and PengeUy, although the 

 continuity has not been actually ascertained, are probably portions 

 of the same band disconnected by some local disturbances. The 

 small patch at Treven connects this last with the larger patches of 

 South Hill, Hay, and Callington, and these, again, with another smaU 

 faulted patch at New Bridge, which last is not very far removed 

 from the line of strike of the volcanic rock of St. Cleer. These 

 patches do not form portions of a continuous bed ; but it is probable 

 that they all belong to the same horizon, judging from the general 

 relations of the rocks of the district — the bed of volcanic rock at 

 St. Cleer on the south bearing very much the same relation to the 

 granite that that of Alternan does on the north, lower rocks being 

 brought up in the interval on the east of the granite at Caradon, 

 Notter Tor, and BondwaU's Mill. On the east of these lower rocks, 

 the country around Linkinghorne and South Hill, which is on the 

 line of upheaval between the Brown-Willy granite and Hingston 

 Down, is thrown down by the faults at Hay and the Redmoor Mine, 

 and with it a patch of the Culm-measures, in the same manner that 

 * Kep. pp. 80-81. 



