90 LIVERPOOL BIOLOGICAL SOCIETY. 
district, which has been recently re-investigated by 
Professor Lewis. South Barrule is a hmestone hill in the 
Isle of Man, four and a half miles north of Castletown ; 
it is 1585 feet high and glaciated to its very summit, 
close to which occur boulders of granite from a boss 
760 feet high, a mile and a half to the E.N.E.; thus here 
we have a proof of an elevation of ice-borne boulders of 
825 feet within a mile and a half, or 950 feet to the mile. 
Similar cases could easily be multiplied, as that quoted by 
Professor James Geikie* from Sdérnebohm, in which blocks 
occur 4500 feet above the sea which are not known in situ 
above 1800 feet. The objections to the explanation of 
these phenomena by floating ice are well summarized by 
Geikie in this paper. Thus there seems no insuperable 
difficulty in the ascent of the ice up this comparatively 
trivial slope, and especially when we remember that the 
ice sheet was probably 1200 feet or more thick, so that 
it merely lapped against the side of the hill, and the upper 
layers of ice rode over it. 
The great argument for the submergence has, however, 
always been the Moel Tryfaen fossils, whose evidence 
seems considerably overrated. The shells are rare and 
fragmentary, and many collectors who have visited the 
section have returned without a single specimen, and 
even men who have devoted some time there have been 
rewarded by but a few fragments which could only be 
identified by a trained specialist. The lists include a 
motley collection from every zone and depth; there are 
shells so littoral as Mytilus edulis, Cardium edule, Litto- 
rina littorea, and especially Littorina rudis, which is 
expressly regarded by Gwyn Jeffreys+ as characteristic of 
* Note on the occurrence of erratics at higher levels than the rock masses 
from which they have been derived. Trans. Geol. Soc., Glasgow, vol. iv., p. 235. 
+ Brit. Conchology, vol. i., p. 104. 
