mineral are all the results of the agency of one Mind, and 

 that a Mind of benevolence and perfect wisdom. 



It will be seen that for several of the facts and conclusions 

 adduced in this paper, I am indebted to the writings of 

 organic chemists of our own day ; more particularly of 

 Liebig, Dumas, and Boussingault, whose penetration and 

 research have disclosed to us so many facts before hidden, 

 relating to the more remote and intimate changes which take 

 place in the performance of the functions of organised beings. 

 Besides these, the views of botanists and physiologists of 

 our own country have been likewise considered. 



Our planet is, at the present day, surrounded by an 

 atmosphere, of which the chemical composition is clearly 

 ascertained ; and a comparison of modern analysis with those 

 of earlier chemists, prove that this chemical composition is 

 fixed and permanent, being 79 parts of nitrogen, 21 of 

 oxygen, and about ^-q part by measure of carbonic acid, in 

 100 parts. 



But there are strong reasons to believe that at earlier 

 periods in the geological history of our globe, the surround- 

 ing atmosphere was much more strongly impregnated with 

 carbonic acid gas than at present. Such a condition of the 

 atmosphere, though incompatible with the existence of the 

 more highly developed and hot-blooded animals, would be 

 favourable to a more rapid and luxuriant growth of plants 

 than can be supported by an atmosphere having the com- 

 position of that which we now respire. Accordingly, we 

 find in the coal which now forms so important an article of 

 fuel, the evidence and the remains of so luxuriant a vegetation. 

 " It was the conjecture of M. Brongniart, in the first 

 instance from the study of fossil botany, and from other 

 geological observations, that the atmosphere, at the time of 

 primitive vegetation, was far more charged with carbonic 

 acid than it is now, and that it was this which not only 



