300 M. Ami Boue on the Paloeohydrography 



continents under the form of islands. In the Atlantic similar 

 indications of older islands exist. At last at the poles great 

 subsidences may have been produced by the force which 

 tended to flatten these ; the many Polar islands may also have 

 been derived from it. But the Arctic lands possess a more 

 powerful agent of change than the Antarctic ; many large 

 rivers flow into the Arctic, and produce every year great 

 motions in the ice-fields ; in the Antarctic, snow and ice alone 

 exercise their powers, and the temperature is not so low as 

 at the opposite pole, but the winter is eternal. The parti- 

 cular external form of the Austral Polar continent, with its 

 two points and re-entering angles, have been adduced by 

 Hombron as proofs of their ancient separation from the 

 southern continents (Compt. Ac. d. Sc, Paris, 1844, v. 18, 

 p. 2). When we arrive at the following interesting conclu- 

 sions, we unite to the preceding great subsidences in the 

 oceans, the greatest continental elevations, not only as chains 

 but also as vaults of whole continents ; and take besides as 

 true, and probably founded on physico-magnetical laws, the 

 well-known doctrine of M. Leblanc, that each direction of 

 elevation cuts the preceding under a right angle, or at least 

 under a very great one (Bull. Soc. Geol. de Fr., 1840, v. 12, 

 p. 140). Without going through all the elevation periods 

 either of MM. Leblanc or Beaumont, we may remain satisfied 

 with shewing that the active and extinct volcanoes of South- 

 Eastern Asia, as well as those of Mexico, Guatemala, and 

 Oregon, cut transversely the older chains of those countries. 

 Elie de Beaumont remarked, besides, that the various eleva- 

 tions in America have changed invariably their positions 

 from east to west ; but quite the contrary happened in Asia 

 and Europe, where this change took place from north to 

 south (Compt. B. Ac. d. Sc. Paris, 1843, vol. 17, p. 415). 



We have thrown some light on the nature of Polar countries, 

 where ice and snow have nearly stopped every formation 

 newer than the old coal formation, and have preserved us a 

 picture of the state of land and water in that remote period. 

 On the other hand, the great subsidences in the Atlantic to 

 the west of Europe and Africa, are inclined from north to 

 south, and seem to have taken place chiefly after the old 



