THE PLAN OF THE EARTH AND ITS CAUSES. 371 



THE PERMANENCE OF CONTINENTS. 



That Lord Kelvin's nebulous segregations, Professor Darwin's primi- 

 tive wrinkling, Sir John Lubbock and Professor Lapworth's double 

 folds are all true causes seems probable. What is doubtful is whether 

 any extensive traceof their influence can be discerned in the present dis- 

 tribution of land and water. A map of the world in early Cambrian 

 times might show the influence of these pregeologieal incidents; but 

 their geographical effects seem to have been obliterated by the changes 

 of geological times. 



Reference to such changes reminds us that we cau not assume their 

 occurrence without considering the unending controversy as to the 

 supposed permanence of oceans and continents. 



There are, it must be conceded, many weighty arguments in favor of 

 the permanence hypothesis. Many of the last great mountain foldings 

 follow the lines of much older movements; and if the mountain axes, 

 the "backbones of the continents," have occupied the same positions, 

 why not also the continents molded upon them? Again, some of the 

 great mountain chains, such as the Andes, run parallel to the nearest 

 shore line, as if the movements that formed them had been deflected 

 by the ocean basin. 



The character of the ocean floors, moreover, suggests that they have 

 never been continental, as they are at present covered by deposits not 

 known in the interior of the continents, and as they are supported by 

 material much heavier than that which forms the foundations of the 

 continents. 



These arguments, however, are not conclusive. Great earth move- 

 ments of one date often cut obliquely and transversely across those of 

 earlier periods. Thus the old northwesterly and southeasterly move- 

 ments of France and Spain have been cut across by the east and west- 

 ern movements of the Pyrenean-Alpine system. Mountain axes have 

 not always been deflected by or limited by existing ocean basins. Thus 

 the north Atlantic basin cuts directly across the old Hercyniau moun- 

 tain chains, which may at one time have extended across the whole 

 Atlantic channel. This is rendered probable by three lines of evidence. 

 Thus in northwestern France, aud in the south of the British Isles, there 

 is a series of ranges trending north of west which is cut off abruptly 

 by the Atlantic slope. On the opposite shore of the Atlantic in New- 

 foundland there is a similar series of truncated ranges formed at the 

 same age as those of western Europe, and having the same trend. 

 Bertrand maintains (1887) that the resemblance between the opposite 

 mountain series is so striking that they should be regarded as parts of 

 one mountain system, of which the central part has been sunk below 

 the Atlantic. The well-known telegraph plateau on which the cables 

 rest may mark the site of this sunken land. Palaeontological evidence 

 also supports the formation of the Atlantic by subsidence; for a shal- 



