422 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 22, 



the faults of Cotele and Pentre Cross have thrown down the countiy 

 about St. Mellion. To the south of St. Ives, however, we come into 

 a belt of country the structure of which is very difficult to unravel, 

 owing to the obscurity of the bedding, the planes of cleavage being 

 so much more strongly marked than the lamination. Thus at Ten- 

 creek, near Liskeard, and at Hepple Mill, near Quethiock, vertical 

 bedding, in which the stratification is shown by seams of ochreous 

 material, is seen cleaved by planes which dip to the south at an 

 angle of 12° ; and at Pope's Mill .horizontal beds are cleaved at an 

 angle of 35°, dipping in the same direction ; but in the great ma- 

 jority of the exposures it is impossible to ascertain whether the 

 laminae are those of deposition or of cleavage"^. It would appear, 

 however, that the argillaceous rocks, with their included beds of 

 volcanic ash &c., are here thrown into a series of narrow east and 

 west plications, which succeed each other in an oblique line extend- 

 ing from the neighbourhood of St. Neots to Saltash on the Tamer ; 

 but the details are involved in intricacy, as one anticlinal axis dove- 

 tails in between others in a manner that renders it difficult to foUow 

 the beds along their strike for any distance. A synclinal axis, how- 

 ever, crosses the Temple branch of the Powey below Panter's Bridge, 

 and runs eastward to Mount Coldwind, north of the Doubleboys 

 railway-station, beyond which it ceases to be recognized. The rocks 

 on the north of Quethiock and Liskeard dip to the south, under beds 

 which are fossiliferous at the railway- station and at the slate-quarry 

 south of Pope's Mill, where they include a bed of argillaceous lime- 

 stone three feet in thickness, first noticed by the late Mr. Giles t. 

 These beds rise again to an anticlinal axis at Menheniot, which 

 runs eastward between the ash-beds at Combe ; and this is succeeded 

 by a synclinal trough at Tilland slate -quarry, in which the beds are 

 highly inclined (60° to 80°), and the slates sometimes blue or 

 purplish. A sharp anticlinal axis foUows, which extends from 

 Menheniot railway-station, by Molenick and ITotter Mill, to Botes 

 Pleming, beyond which there is a synchnal trough ranging from the 

 north of St. Luke's by Landrake, and across the Tamer to the north 

 of St. Budeaux, containing highly inclined grey, blue, and purple 

 slates, which appear to form one or more subordinate anticlinal 

 folds. One of these minor folds occurs at Stoketon, and is on the 

 same line of strike as the axis south of Tamerton Poliot, noticed by 

 Prof. Phillips J, and another at Trematon. The slates and volcanic 

 rocks of Saltash and St. Stephens rise on the south of the latter 

 trough, but they appear to constitute rather a series of plications 

 than a single axis. It would appear, therefore, either that the 

 lamination is deceptive and does not represent the true bedding, or 

 that the plications must be very numerous, even more so in fact than 

 the above description would imply ; otherwise the prevalence of ver- 

 tical and highly inclined stratification over a distance of three or 



* The age of the cleavage is clearly subsequent to the period when the beds 

 were brought into their present position, and therefore to the upthi"ust of the 

 granite. See also De la Beche, Rep, p. 279. 



t Thirty-sixth Ann. Eep. of the Geol. Soc. of Cornwall. ; Pal. Pos. p. 199. 



