GEOLOGY. 547 



CARBONIFEROUS PERIOD. Later on, the first layers that 

 cooled down became covered with a luxuriant vegetation, 

 the fossilized remains of which now constitute our coal-beds, 

 antediluvian forests, which the genius of man extracts 

 from the depths of the earth, to serve the wants of industry 

 and his own dwellings. 



During this period the whole surface of the globe was 

 covered with strange and dense forests, where proudly 

 reigned a host of plants, the representatives of which at 

 the present day play but a very humble part. Here were 

 palms and bamboos, there gigantic Lycopodia, which, now 

 humble creeping herbaceous plants, at that time bore 

 straight stems, towering to a height of eighty to a hun- 

 dred feet. Then came the Lepidodendra, the stem of which 

 reminds one of a reptile's scaly cuirass. Lastly came trees 

 of the family of our Conifers, their boughs laden with fruit. 



These vast primeval forests, which the course of ages was 



impart the perception of light to crustaceans now living at the bottom of the 

 sea. 



" With respect to the waters wherein the trilobites maintained their existence 

 throughout the entire period of the transition formation, we conclude that they 

 could not have been that imaginary turbid and compound chaotic fluid, from the 

 precipitate of which some geologists have supposed the materials of the surface of 

 the earth to be derived, because the structure of the eyes of these animals is such 

 that any kind of fluid in which they could have been efficient at the bottom must 

 have been pure and transparent enough to allow the passage of light to organs of 

 vision, the nature of which is so fully disclosed by the state of perfection in which 

 they are preserved. 



" Regarding light itself, also, we learn from the resemblance of these most an- 

 cient organizations to existing eyes that the mutual relations of light to the eye 

 and of the eye to light were the same at the time when crustaceans endowed with 

 the faculty of vision were first placed at the bottom of the primeval seas as at the 

 present moment." 



