CHAPTER YI 



GEOGRAPHICAL AND GEOLOGICAL CHANGES : THE 

 PERMANENCE OF CONTINENTS 



Changes of Land and Sea, their Nature and Extent — Shore-deposits and 

 Stratified Rocks— The Movements of Continents — Supposed Oceanic 

 Formations ; the Origin of Chalk — Fresh-water and Shore-deposits as 

 proving the Permanence of Continents — Oceanic Islands as indications 

 of the Permanence of Continents and Oceans — General Stability of 

 Continents with constant Change of Form — Effect of Continental 

 Changes on the Distribution of Animals — Changed Distribution proved 

 by the Extinct Animals of Different Epochs — Summary of Evidence 

 for the general Permanence of Continents and Oceans. 



The changes of land and sea which have occurred in par- 

 ticular cases will be described when we discuss the origin 

 and relations of the faunas of the different classes of islands. 

 We have here only to consider the general character and 

 extent of such changes, and to correct some erroneous 

 ideas which are prevalent on the subject. 



Changes of Land and Sea, their Nature and Extent. — It is 

 a very common belief that geological evidence proves a 

 complete change of land and sea to have taken place over 

 and over again. Every foot of dry land has undoubtedly, 

 at one time or other, formed part of a sea-bottom, and we 

 can hardly exclude the surfaces occujiied by volcanic and 

 fresh- water dejoosits, since, in many cases, if not in all, 

 these rest upon a substratum of marine formations. At 

 first sight, therefore, it seems a necessary inference that 

 when the present continents were under water there must 



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