TRANSACTIONS OF SECTION E. 795 



in other latitudes the reverse would appear to be the case, points out that this is 

 in harmony with his -view of a periodical flux and reflux of the ocean between the 

 equator and the poles, lie thinks that we have no evidence of any vertical eleva- 

 tion afftscting wide areas, and that the only movements of elevation that take 

 place are those by which mountains are upheaved. The broad invasions and 

 transgressions of the continental areas by the sea, which we know have occurred 

 again and again, are attributed by him to secular movements of the hydrosphere 

 itself. 



Apart from all hypothesis and theory, we learn that tlie surface of the sea is 

 not exactly spheroidal. It reaches a higher level on the borders of the continents 

 than in mid-ocean, and it varies likewise in height at difPercnt places on the same 

 coast. The attraction of the Himalaya, for example, suffices to cause a difference 

 of 300 feet between the level of the sea at the delta of the Indus and on the coast 

 of Ceylon. The recognition of such facts has led Penck to suggest that the sub- 

 mergence of the maritime regions of North-west Europe and the opposite coasts of 

 North America, which took place at a recent geological date, and from wliich the 

 lands in question have only partially recovered, may have been brought about by 

 the attraction exerted by the vast ice-sheets of tlie Glacial period. But, as Dry- 

 galski. Woodward, and others have shown, the heights at Avhich recent marine 

 deposits occur in the regions referred to are much too great to be accounted for by 

 any possible distortion of the hydrosphere. The late James Croll had previously 

 endeavoured to show that the accumulation of ice over northern lands during 

 Glacial times would suffice to displace the earth's centre of gravity, and thus cause 

 the sea to rise upon the glaciated tracts. More recently other views have been 

 advanced to explain the apparently causal connection between glaciation and 

 submergence, but these need not be considered here. 



Whatever degree of importance may attach to the various hypotheses of secvilar 

 movements of the sea, it is obvious that the general trends of the world's coast-lines 

 are determined in the first place by the position of the dominant wrinkles of the 

 lithosphere. Even if we concede that all ' raised beaches,' so called, are not neces- 

 sarily the result of earth-movements, and that the frequent transgressions of the 

 continental areas by oceanic waters in geological times may possibly have been 

 due to independent movements of the sea, still we must admit that the solid crust 

 of the globe has always been subject to distortion. And this being so, we cannot 

 doubt that the general trends of the world's coast-lines must have been modified 

 from time to time by movements of the lithosphere. 



As geographers we are not immediately concerned with the mode of origin of 

 those vast wrinkles, nor need we speculate on the causes which may have deter- 

 mined their direction. It seems, however, to be the general opinion that the con- 

 figuration of the lithosphere is due simply to the sinking-in and crumpling-up of 

 the crust on the cooling and contracting nucleus. But it must be admitted that 

 neither physicists nor geologists are prepared with a satisfactory hypothesis to 

 account for the prominent trends of the great world-ridges and troughs. Accord- 

 ing to the late Professor Alexander Winchell, these trends may have been the 

 result of primitive tidal action. He was of opinion that the transmeridional pro- 

 gress of the tidal swell in early incrustive times on our planet would give the 

 forming crust structural characteristics and aptitudes trending from north to south. 

 The earliest wrinkles to come into existence, therefore, would be meridional or 

 Bubmeridional, and such, certainly, is the prevalent direction of the most con- 

 spicuous earth-features. There are many terrestrial trends, however, as Professor 

 Winchell knew, which do not conform to the requirements of his hypothesis ; but 

 such transmeridional features, he thouglit, could generally be shown to be of later 

 origin than the others. This is the only speculation, so far as I know, which 

 attempts, perhaps not altogether unsuccessfully, to explain the origin of the main 

 trends of terrestrial features. According to other authorities, however, the area 

 of the earth's crust occupied by the ocean is denser than that over which the con- 

 tinental regions are spread. The depressed denser part balances the lighter elevated 

 portion. But why these regions of different densities should be so distributed no 

 one has yet told us. Neither does Le Conte's view, that the continental areas and 



