THE GEOLOGY OF THE ENGLISH CHANNEL. 167 



three miles in breadth (see p. 144) ; it is quite possible that similar 

 rock in small quantity may occur outside tliis area and have been 

 overlooked. M. 14j has been taken as the type. Possibly these 

 slates are carboniferous ; they more resemble the carboniferous series 

 lithologically than the Devonian. It is to be noted that side by side 

 with these slates occurs a red felsite, and red granites occur also. This 

 distinctly looks like an area where the contact plane of the granite 

 and the sedimentary rock is near to or reaches the surface. Felsites 

 and red-coloured granites would be expected near the junction. If 

 these slates are carboniferous, then the granite is post-carboniferous ; 

 if Devonian, the granite is post-Devonian, in any event not pre- 

 Devonian. Some interesting features attend this area of altered rock. 

 It is true that Hunt's H. 19 granite in situ occurs 20 miles S.W. 

 of Eddystone. Here, too, have been found the only specimens of 

 schorlaceous granite or aplite M. lie, M. 27x ; hence come the other true 

 aplites M. 24g, M. 14e, M. 34e ; and hence we derive the micro-peg- 

 matite, M. 11a., all granitic, and not dioritic rocks. The only schorl 

 rocks, except M. 14f and M. 72, come, however, from M. 31 and M. 36, 

 one to two miles north of this area, and possibly in the absence of M. lie, 

 M. 27x would be regarded as strays. Such was the writer's first thought ; 

 but considering the nature of the adjacent rocks, he now inclines to 

 believe that both schorl rock and schorlaceous granite truly belong 

 to the area. The presence, in addition to the above-named, of diorite, 

 quartz diorite, and some intermediate igneous rocks is not overlooked. 



The areas of gneiss and altered slate lie side by side, but neither 

 can claim exclusive occupation of its portion of the bed of the 

 Channel. (Plate XIV.) 



Since very little good can result, with the present materials, from 

 any further attempt to deal with the plutonic and metamorphic rocks, 

 we next turn to the New lied Sandstone, which overlaps and partially 

 overlies the district just considered. 



NEW RED SANDSTONE. 



The westernmost shore exposures of New Eed Sandstone are at 

 Thurlestone in Bigbury Bay, and in Cawsand Bay on the Mount 

 Edgcumbe shore. There is also on the beach at Drake's Island in 

 Plymouth Sound an untravelled block of breccia of Triassic aspect, 

 weighing about four or five tons. 



The mica-andesite (felsite of the Geological Survey) at Withuoe in 

 Whitsand Bay is an intrusive rock, evidently connected with the red 

 trap in Cawsand Bay, and undoubtedly of New Pted age. 354/4b 

 6 1 miles W. from Eame Head lies on another exposure of this same 

 igneous series. 



NEW SEKIES. — VOL. VIII. NO. 2. M 



