62 F. Chapman — For aminiferal Limestones from Egypt. 



surface cannot rebound beyond the level appropriate to its specific 

 gravity, but is likely through friction to halt somewhat below that 

 point. 



It is probable that the return of the plastic substratum after the 

 load has been removed is not at a uniform rate, perhaps because 

 of halts in the recession of the ice or even of temporary advances 

 during the time of general retreat ; and thus the successive marine 

 terraces found, for instance, on the lower St. Lawrence would be 

 accounted for. 



One other point seems worthy of discussion, as to whether the 

 pre-Glacial and Interglacial elevation of the north-east of America 

 was sufficient to account for an Ice Age without other aid. The 

 evidence of the submerged channels of the St. Lawrence and other 

 rivers points to a former elevation of about 3,000 feet above the 

 present level. It is doubtful if that would place Labrador above 

 snow-line under existing climatic conditions, since the present level 

 of the country is not more than one or two thousand feet. Snow-line 

 in the Eocky Mountains and Selkirks at the same latitude ranges 

 from 9,000 to 7,500 feet ; and even with the difference due to cold 

 oceanic currents, 4,000 or 5,000 feet seems too low an average level 

 for perpetual snow in central Labrador. 



The elevation of Scandinavia, where there are now mountains 

 8,000 feet high, with numerous snowfields 3,000 or 5,000 feet 

 higher, would no doubt under present conditions produce a great 

 extension of the ice, perhaps covering most of the land ; but would 

 it push ice-sheets across the Baltic and North Sea to Germany and 

 England ? This seems very improbable ; and some supplemental 

 cause should perhaps be sought for, but a discussion of such wide 

 questions would lead us too far. 



III. — On an J.?i;eoZma-LiMESTONE and Nummulitic Limestones 



FKOM Egypt. 



By Fredebick Chapman, A.L.S., F.R.M.S. 



Part I. 



THE following description of Egyptian foraminiferal limestones 

 is based on a series of specimens transmitted to me by 

 Dr. H. Woodward, F.E.S., on behalf of Captain H. G. Lyons, F.G.S. 



The series comprises specimens from the Eocene and Miocene 

 of the eastern side of the Eed Sea Hills, collected by Mr. Thomas 

 Barron, E.G.S. ; and specimens from the Eocene of the east side 

 of the Nile, between Assiut and Qena, and from the Baharia and 

 Farafra Oases, collected by Mr. H. J. L, Beadnell, F.G.S. A great 

 amount of interest attaches to these rocks, both as regards their 

 general character and preservation, and also with respect to their 

 microzoic contents. 



The present series of rock-specimens may be described as 

 follows : — 



