330 PRE-DETERMINATION IN NATURE 



nate additions, more especially upon their edges and their 

 hollows, so that while there has been a constant process of 

 removal of material from the higher parts of the land, and 

 deposition in the sea, and while there have been periodical 

 elevations and subsidences, the great areas of land and water 

 have remained substantially the same, and the main lines of 

 elevation and folding have conformed to the directions origin- 

 ally fixed. Thus, in regard to the dry land itself, there has 

 been fixity, on the one hand, and mutation on the other, of a 

 most paradoxical aspect, till we understand something of the 

 great law of constant change united with perennial fixity in 

 nature. From want of attention to this, the permanence of 

 continents is still a debated question, and it is difficult for 

 many to understand how the frequent dips of the continental 

 plateaus and margins under the sea, and their re-elevation, 

 often along with portions of the shallower sea bottom, can be 

 consistent with a general permanence of the position of the 

 continents and of the corresponding ocean abysses ; yet, when 

 this is properly understood, it becomes plain that the union 

 of fixity with changes of level has been a main cause of the 

 continuity and changes of organic beings. Only the submerg- 

 ence of inland plateaus under shallow and warm waters 

 could have given scope for the introduction of new marine 

 faunas, and only re-elevation could have permitted the greatest 

 extension of plants and animals of the land. Thus, the con- 

 tinuity of life with continual advance has depended on the 

 permanent existence of continental and oceanic areas ; and 

 the continents that remain to us with all their diversity of 

 elevation and outline, their varied productions, both mineral 

 and organic, and their life, which is a select remainder of all 

 that went before, have been produced and furnished by a 

 succession of changes, modified by the most conservative 

 retention of general arrangements and forms. 



It is evident, however, that it is not merely permanence we. 



