268 THE GEOLOGICAL STRUCTURE OF SOUTH CORNWALL. 



me state that I consider it extremely doubtful if any of these 

 Ladock beds really belong to the Devonian at all. There is no 

 fossil evidence whatever to show that they do, and their 

 strategraphical position would also seem to negative the idea. 



It is quite possible that the very highest of these Ladock 

 beds may not be far from, or even form the base of the 

 Devonian, but at all events, it is not until we reach the neigh- 

 bourhood of St. Austell that we meet with strata of undoubted 

 Devonian age containing characteristic fossils, in spite of which, 

 by the way, Mr. Collins indicates the strata of this area in his 

 map as of Lower Silurian age. 



Taking then into account the whole of the strategraphical 

 evidence, and the non-occurrence of fossils in these rocks, a fact 

 so highly characteristic of the beds which we have already 

 described as Lower Silurian, as they are developed in this por- 

 tion of Cornwall, I think we are fully justified in regarding these 

 Ladock rocks simply as an upper portion of the Lower Silurian 



We have already noticed the fact that the thick bed of 

 conglomerate occurring south of the Helford river, at the Nare 

 Point, which Mr. Collins claims to be a detached or outlying 

 portion of his Ladock formation, is really after all but part of 

 the Lower Silurian of that district, strictly conformable with the 

 other conglomerates which make up that well marked group. 



Two other localities are cited where his Ladock formation 

 is stated to be seen resting unconformably on the edges of the 

 the Lower Silurian. Both are on the coast, one a little south of 

 Pentewan, and the other at Chapel Point, near Mevagissey. Both 

 of these localities were visited and examined, but no evidence of 

 unconformability could be detected. The rocks in this neigh- 

 bourhood are certainly much disturbed, but there is nothing 

 which can be regarded as an unconformability. 



Altogether I think it will be very clear to any physical 

 geologist that instead of these Ladock beds forming, as stated 

 by Mr. Collins, ' ' the most recent stratified rocks of Central and 

 West Cornwall," it will, I think, be found that they are in 

 reality about the lowest in the county, and are covered by the 

 great thickness of beds running from St. Austell Bay to beyond 

 Looe, which he places beneath his Ladock formation, although 

 the former are well known to run up into the base of the 

 Plymouth limestones. 



