Ch. IX.] RECAPITULATION. 117 



thousand feet above the level of the sea, and this elevation im- 

 plies an extraordinary modification in the state of the earth's 

 crust at some unknown depth beneath the tract so upheaved. 



5thly. The most probable hypothesis in regard to the nature 

 of this change, is the successive generation and forcible intru- 

 sion into the inferior parts of the earth's crust of lava which, 

 after cooling down, may have assumed the form of crystalline 

 unstratified rock, such as is frequently exhibited in those 

 mountainous parts of the globe where the greatest alterations 

 of level have taken place. 



Gthly. Great inequalities must have been caused on the 

 surface of the new-raised lands during the emergence of the 

 newer Pliocene strata, by the action of tides, currents, and 

 rivers, combined with the disturbing and dislocating force of 

 the elevatory movements. 



7thly. There are no features in the forms of the valleys and 

 sea-cliffs thus recently produced, which indicate the sudden 

 rise of the strata to the whole or the greater part of their pre- 

 sent altitude, while there are some proofs of distinct elevations 

 at successive periods. 



Sthly. We may infer that the species of terrestrial and 

 fluviatile animals and plants which now inhabit extensive 

 districts, formed during the newer Pliocene era, were in exist- 

 ence not only before the new strata were raised, but before 

 their materials were brought together at the bottom of the sea. 



