266 THE GEOLOGICAL STRUCTURE OF SOUTH CORNWALL. 



conglomerate* which forms the Nare Point, altogether from the 

 Lower Silurian, and has placed it in his Ladock or Devonian 

 formation. This he has done on the ground of another alleged 

 unconformability, said to be seen near the Nare Point, of which 

 a diagram is given plate, A, fig. 2, which represents this con- 

 glomerate as resting on the upturned edges of the Lower 

 Silurian. 



Anyone who carefully examines this section at the Nare 

 Point will find that Mr. Collins has completely misinterpreted 

 the relation of the conglomerate to the rest of the beds, many 

 of which are of a similar nature. The conglomerate certainly 

 rises high above the accompanying strata, forming an eminence 

 a little way inland from the Point, but this eminence is entirely 

 due to its possessing greater hardness than the adjoining slaty 

 rocks. It is distinctly interstratified and inclines at the same 

 angle and in the same direction as the other beds, and can be 

 traced down to the shore, where its relations with the other strata 

 are seen to be strictly conformable, forming along with other beds 

 of conglomerate and slates, an unbroken and consecutive series 

 of beds. 



There are a few other points connected with these Lower 

 Silurian rocks with which I cannot agree, such as relate to the 

 distribution and boundaries of the system, but these must form 

 a subject for some future communication. In the meantime let 

 us pass to the consideration of the beds termed Upper Silurian. 



Upper Silurian. — Under this head Mr. Collins includes the 

 great series of strata occurring in the neighbourhood of Powey, 

 Lantivet Bay, Polperro, &c , so well known from the remarkable 

 fossils of fish and other remains first found in them by Peach, 

 and the late able naturalist, Dr. Jonathan Couch of Polperro. 



Here again Mr. Collins brings in other unconformabilities 

 separating this formation from the underlying Lower Silurians, 

 but where any of these unconformabilities occur is not stated. 

 As far as my researches extend I have not been so fortunate as 

 to come across any clear indications of unconformability. 



Lithologically these beds consist of a great series of thickly 

 bedded impure sandstones, black, grey, purple, and red slates, 



* Subsequent investigations indicate these to be true ashes or tuffs and 

 agglomerates. 



