THEORY AND PRACTICE. 69 



Of all the practical illustrations that ever appeared 

 contemporaneously with the announcement of a great 

 doctrine, the introduction and use of Guano during 

 the lifetime of Liebig is one of the happiest and most 

 remarkable. If some great physical event had testi- 

 fied to men's bodily senses the motion of the Earth 

 round the Sun, and the steady centricity of that 

 luminary, during the exact lifetime of Copernicus or 

 Galileo ; or if some conceivable reflection of the 

 earth's surface in the deep azure of heaven, had ex- 

 hibited to men's wondering eyes the outline of the 

 great American continent looming along its obverse 

 hemisphere, just as Columbus had departed in search 

 of it, they would not each have furnished a more 

 triumphant vindication of the achievements of those 

 master-minds, during their own existence, than that 

 which the more fortunate Professor of Giessen has 

 been destined to witness. No sooner had the perse- 

 cuting infidelity of man (the same in every age) be- 

 gun to crucify the great doctrine of THE NUTRITION 



OF PLANTS FROM THE ATMOSPHERE, than the USe 



of Guano and of inorganic manures began to give it 

 proof. f Burn a plant, whether it be an Oak-tree or 

 a stalk of Clover ' (for so the assertion of the great 



v O 



Analyst may be briefly epitomised), ' and the trifling 



