610 PEOCEEDIXGS OE THE GEOLOGICAL SOCIETY. 



5. Lee and Morte Bay. — At Lee the lower calcareous fossiliferous 

 member of the Ilfracombe group is succeeded by the upper or non- 

 fossiliferous, grey, smooth, glossy slates of Morte, whose physical fea- 

 tures are totally distinct from those to the north or south, and which 

 nearly equal in thickness the Upper Old Red Sandstones overlying 

 them, viz. from Woolacombe, Osborough, West Down, and Potter's 

 Hill on the north side, to Yention and Pickwell on the south. Prom 

 Bull Point, west of Lee Bay, through Rockham Bay, the smooth argil- 

 laceous slates dip south at a mean angle of 40°, with cleavage at an 

 angle of from 60° to 70° south ; a remarkable system of white amor- 

 phous quartz veins traverses these Rockham Bay slates, chiefly along 

 their stril^e, from east to west, or obliquely to it ; these veins are due 

 probably to fracture and subsequent infiltration by segregation. The 

 undulations and folding of the slates here are continuous, numerous, 

 and traversed by cleavage ; and this continues in various degrees to 

 Morte Point, and south of Mortehoe, where again a system of east 

 and west white quartz veins, 2, 4, and 6 feet thick, traverses the 

 vertical slates up the valley to Twitchim. Reefs also stretch out to 

 sea, dipping at very high angles (var3dng from 70° to 80° S.W.), and 

 with cleavage nearly coincident (60° to 70°*) with the bedding. 



'Eo one who has not examined this section between Lee, Rockham, 

 Hortehoe, and the rivulet that descends to the shore from Twitchim, 

 can tell how difficult it is to work out either the dip or cleavage- 

 sj^stem in these slates f. In the elevated ridge of ground about 

 the hamlet of Yard, and continuous with Morte Point to the 

 east, they are rolled and form an anticlinal ; this ridge is the axis 

 or watershed to the country north and south of it, all the streams 

 taking their rise in this down and falling on either side to the 

 sea. The total absence of this great series of slates to the south 

 of Pickwell Down, with their attendant conditions and position 

 above the calcareous group of Ilfracombe, is significant, when treat- 

 ing either of the supposed fault (against w^hich they ought to 

 abut, or their absence should be accounted for) or the anticlinal 

 which, if either existed, should repeat them to the south, where, 

 be it remembered, no vestige of them occurs. The Morte series 

 gives proof of deep-sea accumulation and is unfossiliferous, whereas 

 the Tipper Devonian beds that rest upon the Upper Old Red 

 Sandstones of PickAvell Down are crowded with organic remains, 

 having been deposited under shallow-sea conditions, and having 

 few species in common with the lower beds and those that 

 live on or pass into the Carboniferous series as gradually as the 

 physical changes oscillate also ; and a greater contrast amongst 



'^ This system of quartz veins traverses all North Devon (east and v^^est), 

 from Oatliampton quarries, near Wiveliscombe, to Morte Bay, occurring again 

 at Lundy Island, where they traverse the same slates, and under the same con- 

 ditions, intersecting like network the grey glossy slates of the "Eattles," 

 " Lamatory," and Rat Island— at the southern end of that remarkable island, 

 where trap dykes and quartz veins vie Math each other in their ramifications, 

 the former traversing the granite also, in all directions and at all angles. 



t It is most difficult to distinguish cleavage-planes from bedding in these 

 slates. 



