CHAPTER VI. 



GEOGEAPHICAL AND GEOLOGICAL CHANGES : THE 

 PEKMANENCE 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 

 particular 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 

 occupied by volcanic and fresh-water deposits, 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 have been other continents situated where we now 



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