264 THE GEOLOGICAL STRITCTTTRE OF SOUTH CORNWALL. 



gneiss among them is a statement to which, we take exception. 

 The band or beds in question are certainly much metamorphosed 

 by their close contact to the granite, but approach in no way 

 whatever the aspect of a true gneiss. The next important 

 feature in connection with these Cambrian rocks is the statement 

 made that they are separated from the overlying Lower Silurian 

 by well marked unconformabilities which occur in various parts 

 of the county, a statement which if correct would fully justify 

 Mr. Collins in applying the term Cambrian to the strata des- 

 cribed by him as such. 



These alleged unconformabilities are said to be seen "in the 

 river just below Devoran at Feock, in the roadside not far from 

 the Church, and at the southern end of Ponsanooth tunnel 

 between Perranwell and Penryn." 



For the express purpose of verifying these statements all of 

 these loca,lities were visited and examined with care but without 

 any trace of the alleged unconformabilities being visible. 



The section given in plate B, fig. 6, accompanying Mr. 

 Oollins's paper, represents an unconformability, as he says it 

 occurs in the Devoran Creek, between Chycoose and Point, but 

 its existence as drawn in the diagram is not to be found in this 

 vicinity. The soft and nearly flat lying beds described by Mr. 

 Collins, and apparently mistaken by him for the Lower Silurian, 

 covering the edges of his highly inclined and contorted 

 Cambrians are, we think, nothing else than broken-up edges, 

 together with the debris swept down from the bank above ; this 

 at all events was the only appearance we could find answering 

 in any way to the diagram or to its description. 



The section as exposed at the south end of Ponsanooth 

 tunnel, where another unconformability is said to occur, was 

 carefully examined, also its north end, but both with a like 

 result, each end exposing a regular and consecutive series of 

 beds without any unconformability whatever, or anything 

 approaching to it occurring. 



The remaining section referred to as exposing an uncon- 

 formability at Feock, in the roadside not far from the Church, 

 betrays no sign of it. All the roadside exposures at and near 

 this point are very much decomposed, broken up, and fallen 

 from their original position, but wherever good sections 



