CHAPTEK XI. 



TERTIARY PERIOD. 



Tertiary System, Supracretaceous Group of English ; Terrains de Sediment 

 Superieurs of French ; Tertiargebilde of German Authors. 



Authors r Lyell, Charlesworth, Webster, Prestwich, Scrope, Horner, Cuvier, 

 Brongniart, Constant Prevost, Wright, &c., &c. 



Collections : Geological Society, those of the Marchioness of Hastings, 

 Mr. Bowerbank, Mr. Saull, Mr. F. Edwards, and Mr. S. V. Wood, 

 Private Cabinets in Suffolk, Norfolk, Isle of Wight, London. 



HAYING described the studies which are essential to the 

 geologist, and suggested the best mode of pursuing them ; 

 we shall now sketch a compendious account of the various 

 geological periods, and the stages into which they are 

 divided. The student will find his inquiries assisted, by 

 impressing on his memory, at an early period of his studies, 

 some striking facts, characteristic of each period and stage, 

 by which they may be recognised. Thus, the varied deposits, 

 fluviatile, lacustrine, marine, and volcanic, which constitute 

 the tertiary system, may be distinguished by the following 

 general features : 



1. They are deposited in depressions, usually of the chalk, 

 and occasionally of the older rocks. 



2. They evince proofs of important changes in the relative 

 level of land and sea. 



3. They afford evidence that, during this epoch, part of 

 Europe was the site of great lakes, which, at the present day, 

 have their analogues in the American continent. 



4. They show that volcanic agency was then developed on 

 a vast and magnificent scale. 



5. They testify the gradual refrigeration which took place 

 during this epoch, and the approximation consequent on 

 change of climate, to the forms of vegetable and animal life 

 prevailing at the present day. 



