LEAVES ON THE ATMOSPHERE. 177 



iy simple an organ as the leaf of a plant. The agency 

 of the vital principle alone can account for these won- 

 ders, though it cannot, to our understanding, explain 

 them. " The thickest veil," says Dr. Thomson at the 

 end of his chapter on vegetation, " covers the whole of 

 these processes ; and so far have philosophers hitherto 

 been from removing this veil, that they have not even 

 been able to approach it. All these operations indeed, 

 are evidently chemical decompositions and combina- 

 tions ; but we neither know what these decompositions 

 and combinations are, nor the instruments in which they 

 take place, nor the agents by which they are regulated." 

 The vain Buffon caused his own statue to be inscrib- 

 ed " a genius equal to the majesty of nature," but a 

 blade of grass was sufficient to confound iiis pretensions^ 



