346 THE PLEISTOCENE PERIOD. 



allowing 4 feet more for the difference from the base of the 

 deposit to its centre (it is a conglomerate overhanging ledge 

 and the underside is taken for the height above high-water 

 mark), we get the mean height of 50 feet. There are many 

 others. 



It has been suggested by our Jersey friends that these 

 two elevations may be but different portions of the same 

 beaches. This is not the case in Guernsey and the following 

 quotation from the last quoted paper of Professor Prestwich 

 disposes of that criticism (fol. 304). 



" It has been suo-o-ested that the raised beaches do not 

 indicate any alteration of level, being merely the remaining 

 portions of the upper parts of the inclined planes up which 

 the shingle was driven by storm-waves ; but amongst other 

 reasons, besides the considerable and varying heights (10 to 

 50 feet) of the beaches on the coast, the double cliffs (Weston, 

 fig. 10 and Porthelms, fig. 12) the presence of Balani attached 

 to the uppermost rocks (Barnstaple Bay), at or above that at 

 which they could possibly have lived . . . clearly show that 

 there has been a change of level." 



Belonging to the group of low-level beaches is one of, in 

 Guernsey, one or two feet above O.D. and in Jersey about 

 10 to 13 feet above O.D., but as this is associated with 

 another proof of change of level, I shall defer the description 

 to a later part of this paper. 



THE HIGHER LEVEL BEACHES. 



The deposits above 60 feet are not assigned by the Jersey 

 co-workers to the same geological period as the lower beaches, 

 and in that I differ from them. As the conclusions to be 

 arrived at are at variance, I shall describe the deposit in this 

 part of my paper and discuss the evidence later on. 



In Guernsey we have four deposits between 60 and 

 75 feet. Three of these might be looked upon as high 

 portions of the 50 feet beaches. I do not think they can be 

 so classified, but the fourth is certainly distinct; hence I think 

 they denote that the sea rose to greater heights, and that we 

 have a true indication of a higher and rising sea-level. 



I shall advance evidence to show that a beach at 

 one time rested on the top of Guernsey ; for the moment I 

 shall simply say that the local clays are filled with pebbles 

 that must have been derived from such a beach. 



THE ERODED PLATFORMS. ' 



As a proof of the different sea-levels the rock-platforms, 

 laud slopes and escarpments offer valuable additional evidence. 



