Essay introductory to Geology. 1 1 



we do find, a greater variety of terrestrial species than heretofore. Insects 

 of all the recent genera, and many species nearly approximating to those 

 still existing, have been discovered. 



The maramiferous remains imbedded in the three tertiary groupes, ob- 

 serve the same progression which we have already noticed in the testacea, 

 extinct palffiotheria, &c. alone occuning in the lowest gronpe ; while the 

 middle groupe exhibits these, with a mixture of the elephants, &c. of our 

 own diluvial gravel ; and the latter class become prevalent in the superior 

 groupe. 



Lastly, the vegetation of this superior geological order approximates in 

 the same degree to that actually existing : it presents the same classes, 

 and in similar proportions, the dicotyledoneae being the more numerous, 

 then tlie monocotyledoneaj, the gymnospermous phanerogameae, and the 

 cryptogamias and agamife taking the last place. The general character of 

 tliis vegetation is that which might be expected to ])revail in extended 

 continents, of which the temperature was perhaps somewhat more elevated 

 than at present ; but considerable local differences may be observed in this 

 respect, such as would naturally arise from varying local causes of unequal 

 temperature, such as dift'erence of elevation, &c. 



These remains often give rise to considerable carbonaceous strata, in 

 which the woody fibre is still to be distinctly recognised as lignite. In some 

 places the middle tertiaries assume characters which might, at first sight, 

 almost be confounded with those of the older coal fields. 



In concluding this rapid survey of the geological distribution of organic 

 remains, we cannot fail to observe, that they very generally indicate the 

 ancient prevalence of a much higher temperature than that which at pre- 

 sent belongs to our temperate climates. We have almost always animal and 

 vegetable forms, which belong to the warmest latitudes ; the coral reefs of 

 tropical seas ; with pentacrinites, like those now found on the coasts of 

 Barbadoes ; the testacea, fish, crocodiles, and turtles, of the same torrid 

 oceans; and in the land, forests of palms and arborescent ferns. And 

 though this is less markedly the case in the Flora of the tertiary period, yet 

 still we find the fish of tropical seas sporting around the coasts; the hippo- 

 potamus, stalking through the rivers ; elephants, rhinoceros, and hyaenas, 

 roaming through the jungles. 



We may conclude these two articles of descriptive geology, namely the 

 order of geological formations and the organic remains which they present, 

 by a synoptical table, calculated to assist the memory. 



