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THE WONDERS OF GEOLOGY. Lect. Vii 



the localities where these forms of vegetation flourish most 

 luxuriantly. But must we therefore infer that the countries 

 in which the carbonaceous flora grew were groups of 

 islands enjoying an intertropical climate? — In the paucity 

 of the graminese or grasses, which form so large a pro- 

 portion of the existing floras, and the predominance of 

 ferns, the vegetation of the coal-measures approaches that 

 of New Zealand, in which the cellulosas form one-third of 

 the whole, and the grasses are very few in number.* 



41. Atmospheric conditions during the Carbonife- 

 rous epoch. — It is remarkable that amidst the luxuriant 

 vegetation which prevailed on the dry lands during the Carbo- 

 niferous epoch, there should not have existed contemporane- 

 ous herbivorous quadrupeds ; but not a relic of any animal 

 of this kind has been discovered in the coal strata. Indeed, 

 with the exception of the Iguanodon of the Wealden {ante. 

 p. 423), no remains of large vegetable feeders have been 

 found in any of the deposits anterior to the eocene, in 

 which first appear relics of the herbivorous pachyderms ; 

 nor even a vestige of phytophagous terrestrial mollusca. 



It was an opinion once very generally entertained, and 

 the idea still seems to find favour,! that previously to and 

 during the carboniferous period, the atmosphere was so 

 charged with carbonic acid gas, as to be unfitted for the 

 respiration of animals of a higher order than reptiles ; and 

 that the dense and luxuriant vegetation of that epoch was 

 designed to purify the air, by elaborating coal, and thus 

 abstracting the superabundance of irrespirable gas, and 

 setting free a corresponding proportion of oxygen: thus 

 rendering the surface of the earth suitable for the existence 

 of terrestrial reptiles, and ultimately of birds and mam- 

 malia. But Mr. Lyell has clearly shown, not only the 

 fallacy of such surmises, but that, so far as we know, if any 



* See Medals of Creation, p. 2U2. 



\ See Professor Owen's Hunterian Lectures, vol. ii. p. 15. 



