RETROSPECT. 411 



which they once grew, subsided to a great depth, 

 and formed part of the bottom of a profound 

 ocean ; the waters of which teemed with countless 

 myriads of zoophytes, shells, and fishes, of species 

 long since extinct. Periodical intrusions of ther- 

 mal streams charged with silex, gave rise to layers 

 and veins of nodular and tabular flint, and occa- 

 sioned the silicification of the organic remains 

 subjected to their influence. 



This epoch, which was of long duration, was suc- 

 ceeded by elevatory movements, by which the 

 bottom of the deep was broken up, and large areas 

 were slowly upheaved ; and as the elevation con- 

 tinued, the deposits which had accumulated in 

 the depths of the ocean, approached the surface, 

 and were exposed to the action of the waves. 

 These masses of cretaceous strata now began to 

 suffer destruction, and the delta of the Country 

 of the Iguanodon gradually emerged above the 

 waters ; and finally the petrified forest of the 

 Oolite rose in the midst of the sea, and became 

 dry land. At length some portions of the ele- 

 vated strata attained an altitude of several hun- 

 dred feet, and a group of islands was formed ; 

 but in the basins or depressions beneath the 

 waters, sediments derived from the disintegration 

 of the sea-cliffs were deposited. Large herbivorous 



B B 



