TRAXSACTIO>'S OF SECTION E. 801 



throughout all the manifold revolutions of the past, would appear to have per- 

 filsted as a more or less well-marked boundary, separating the northern from the 

 southern basin. Daring certain periods it was no doubt in some degree submerged, 

 but never apparently to the same extent as the depressed areas it served to sepa- 

 rate. From time to time uplifts continued to take place along this central belt, 

 which thus increased in breadth, the younger formations, which were accumulated 

 along the margins of the two basins, being successively ridged up against nuclei 

 of older rocks. The latest great crustal movements in our continent, resulting in 

 the uplift of the Alps and other east and west ranges of similar age, have still 

 further widened that ancient belt of dominant elevation which in our day forms 

 the most marked orographical feature of Europe. 



The Russo-Germanic basin is now for the most part land, the Baltic and the 

 North Sea representing its still submerged portions'. This basin, as already re- 

 marked, was probably never so deep as that of the Mediterranean. We gather as 

 much from the fact that while meclianical sediments of comparatively shallow- 

 water origin predominate in the former area, limestones are the characteristic 

 features of the southern region. Its relative shallowness helps us to understand 

 why the northern depression should have been silted up more completely than the 

 Mediterranean. We must remember also that for long ages it received the drain- 

 age of a much more extensive land surface than the latter, the land that sloped 

 towards the Mediterranean in PaloBOZoic and Mesozoic times being of relatively 

 little importance. Thus the crustal movements which ever and anon depressed 

 the Russo-Germanic area were, in the long run, counterbalanced by sedimentation. 

 The uplift of the Alps, the Atlas, and other east and west ranges has greatly con- 

 tracted the area of the Mediterranean, and sedimentation has also acted in the 

 same direction, but it is highly pi'obable that that sea is now as deep as, or even 

 deeper than, it has ever been. It occupies a primitive depression iu which the 

 rate of subsidence has exceeded that of sedimentation. In many respects, indeed, 

 this remarkable transmeridional hollow — continued eastward iu the Red Sea, the 

 Black Sea, and the Aralo-Caspian depression — is analogous, as we shall see, to the 

 great oceanic trough itself. 



In the earlier geological periods linear or axial uplifts and volcanic action 

 again and again marked the growth of the land on the Atlantic sea-board. But 

 after Palnsozoic times no great mountains of elevation came into existence in that 

 region, while volcanic action almost ceased. In Tertiary times, it is true, there 

 was a remarkable recrudescence of volcanic activity, but the massive eruptions of 

 Antrim and Western Scotland, of the Fseroe Islands and Iceland, must be con- 

 .-sidered apart from the general geology of our continent. From Mesozoic times 

 onwards it was along the borders of the Mediterranean depression that great 

 moimtain uplifts and volcanoes chieiiy presented themselves ; and as the laud 

 surface extended southwards from Central Europe, and the area of the Mediter- 

 ranean was contracted, volcanic action followed the advancing shore-lines. The 

 occurrence of numerous extinct and of still existing volcanoes along the borders 

 of this inland sea, the evidence of recent crustal movements so commonly met 

 with upon its margins, the great irregularities of its depths, the proximity of vast 

 axial uplifts of late geological age, and the frequency of earthquake phenomena, 

 all indicate instability, and remind us strongly of similarly constructed and dis- 

 turbed regions within the area of the vast Pacific. 



Let us now look at the Arctic and Antarctic coast-lines of North America. 

 From the extreme north down to the latitude of New York the shores are 

 obviously those of a partially submerged region. They are of the same type as 

 the coasts of North-western Europe. We have every reason to believe also that 

 t he depression of Greenland and North-east America, from which these lands have 

 only partially recovered, dates back to a comparatively recent period. The fiords 

 and inlets, like those of Europe, are merely half-drowned land valleys, and the 

 continental shelf is crossed by deep hollows which are evidently only the seaward 

 continuations of well-marked terrestrial features. Such, for example, is the case 

 with the valleys of the Hudson and the St. Lawrence, the submerged portions of 

 which can be followed out to the edge of the continental plateau, which is notched 



1892. 3 r 



