Formation and Transformation of Continents. 137 



stretching from east to west, backed up by plateaux on their 

 polar or equatorial slopes, according as the denudation has been 

 effected by equatorial or polar currents ; and of secondary areas 

 of elevation, following the direction of the meridian, with their 

 mountain ranges running north and south, backed up by plateaux 

 on their eastern or western slopes. In the case of the secondary 

 areas of elevation, their direction along the meridian exposes 

 them to denudation on both sides by equatorial and polar cur- 

 rents, hence the triangular shape of the present continents with 

 their apex pointed towards the South Pole. Hence also the 

 observed transfer of land from east to west. Both equatorial 

 and polar currents are more powerful along the east coast than 

 along the west coast of the continents, and the deposit of solid 

 matter is in consequence least on the western side of an oceanic 

 basin, greater on its eastern side, and greatest in its centre. 

 This agrees with observed facts, for the western part of an 

 oceanic basin is as a rule deeper than the eastern, while the 

 plateaux are found in the centre. 



Primary areas of elevation are exposed to denudation by 

 equatorial currents upon their equatorial slopes, and by polar 

 currents upon their polar slopes. The former currents being 

 more powerful than the latter, the plateaux predominate upon 

 the polar slopes, as we find it to be the case in the present con- 

 tinents ; but the combined action of both equatorial and polar 

 currents ultimately tends to break through the primary areas of 

 elevation in the direction of the meridian, and to cut them up 

 into separate continents. The latter would then present a com- 

 bination of primary and secondary areas of elevation, with their 

 respective watersheds and mountain ranges running at right 

 angles to each other (Plate 4a). 



Formation of Mountain Ranges and Submarine Ridges. — 

 The application of the previous remarks to the configuration of 

 the continents at present existing on the surface of the globe is 



