THE HUMAN OR PRESENT PERIOD. 525 



the sedimentary series for the remaining distance seems to be com- 

 plicated and imperfect. On the borders of Europe, from the White 

 Sea to the Skager Rack, little beside Archean and Proterozoic ter- 

 ranes appear, while the later terranes are mainly unrepresented. In 

 Scotland, Wales, Ireland, Normandy, and the Spanish peninsula, 

 ancient crystalline rocks, interspersed with Paleozoics, largely occupy 

 the coast or closely approach it. A crystalline belt is represented as 

 lying a little back from the coast throughout nearly the whole extent 

 of the western side of Africa, and this is scarcely less true of the eastern 

 side. Although newer formations lie between this and the coast, 

 they represent, according to present knowledge, but a small part of 

 the post-Proterozoic series. The southern and eastern coasts of Asia 

 are occupied by a much-interrupted succession of various formations 

 in which none are conspicuously dominant, and no systematic series 

 is indicated. The protruding peninsulas of India, Anam, and Korea 

 seem to be largely formed of very ancient terranes, except some little 

 fringings of quite recent deposits. In Australia, crystalline and Paleo- 

 zoic rocks are predominant at or near the eastern coast and along 

 much of the western, and there is little or no suggestion of an 

 encircling belt of sediments systematically representing outward growth 

 of the land. 



And yet in the interior of all these continents there are great series 

 of sediments recording much more fully the progress of the ages. If 

 our knowledge of the progress of events were limited to coast-border 

 series, it would be imperfect indeed. 



None the less, we must believe that the theoretical continent- 

 bordering series exists, and for ourselves we do not question that it 

 is absolutely continuous, in its deeper parts, from the Archean to the 

 present time. There must therefore be agencies in play other than 

 the mere systematic lodgment of sediments about the continental 

 borders, and these agencies have persistently disturbed the border 

 record. If the mutilated record of the border-sedimentation be asso- 

 ciated with the deep trenches of the surface and abysmal slope of the 

 continental shelves, and with the rejuvenated streams and " fall lines " 

 of the tracts lying back from the coasts, a possible solution of the 

 common problem may be found in the habitual mode of behavior of 

 the continental borders. 



