Dr. MantelVs Isle of Wight. 237 



was inhabited by turtles and marine lizards of extinct genera. 

 This country suffered a partial subsidence, which was effected so 

 tranquilly, that many of the trees retained their erect position, 

 and the cycadeous plants, and a considerable layer of the vege- 



table mould in which they grew, remained undisturbed. In this 



state an inundation of fresh\yater covered the country and its 

 forests, and deposited upon the soil and around the trees a calca- 

 reous mud, which was gradually consolidated into limestone; 

 thermal streams, holding flint in solution, percolated the mass, 

 and silicified the submerged trees and plants. 



" A further subsidence took place, floods of freshwater over- 

 whelmed the petrified forest, and heaped upon it accumulations 

 of detritus, which streams and rivers had transported from the 

 land. The country traversed by the rivers, like that of the sub- 

 merged forest, enjoyed a tropical climate, and was clothed with 



palms, arborescent ferns, and cycadeae ; it was tenanted by gigan- 

 tic herbivorous and carnivorous reptiles, and its waters abounded 

 in turtles, and various kinds of fishes and mollusca. The bones 

 of the reptiles, the teeth and scales of the fishes, the shells of the 

 mollusca, and the stems, leaves, and seed-vessels of the trees and 

 plants, were brought down by the streams, and imbedded in the 

 mud of the delta, beneath which the petrified forest was now 

 buried. 



" This state continued for an indefinite period— another change 

 took place — the Country of Reptiles with its inhabitants was swept 

 away, and the delta, and the fossil trees with the marine strata 

 on 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, 

 °f species long since extinct. Periodical intrusions of thermal 

 streams charged with silex, gave rise to layers and veins of nod- 

 ular and tabular flint, and occasioned the silicification of the or- 

 ganic remains subjected to their influence. 



"This epoch, which was of long duration, was succeeded by 

 elevatory movements, by which the bottom of the deep was 

 broken up, and large areas were slowly upheaved ; and as the 

 «levation continued, the deposits which had accumulated m the 

 depths of the ocean approached the surface, and were exposed 

 ^ the action of the waves. These masses of cretaceous strata 

 aow began to suffer destruction, and the delta of the country ot 

 ^e Iguanodon gradully emerged above the waters; and nnaity 

 [he petrified forest of the Oolite rose in the midst of the sea and 

 became dry land. At length some portions of the elevated strata 

 Gained an altitude of several hundred feet, and a group of isl- 

 ands was formed : but in the basins or depressions beneath the 

 haters, sediments derived from the disintegration of the sea-chfts 

 We re deposited. Lar^e herbivorous mammalia now inhabited 



