1864.] CHEMISTRY OP MANURES. 101 



Thus have France, England, and Germany, in the course of 

 about a century, successively produced the three great Lawgivers 

 of Modern Husbandry. 



It was in the year 1837 that the British Association for the 

 Advancement of Science, perceiving the immense accumulation of 

 facts, for the most part unsystematized, which had already taken 

 place in organic chemistry, and was annually increasing therein, 

 invited Justus Liebig, who had already attained to eminence by 

 his extensive researches in this branch of science, to write a report 

 upon its then condition ; which honorable duty the illustrious 

 philosopher undertook. In the year 1840, Liebig, in fulfilment 

 of this engagement, produced his memorable work on " Organic 

 Chemistry in its Applications to Agriculture and Physiology." 

 In ordinary hands such a report would, in all probability, have 

 been but a compilation, more or less compendious, of facts already 

 known, and conceptions already proposed for their co-ordination. 

 But the original genius of Liebig, essentially philosophical and 

 constructive, impressed upon his work a very different character. 



He began by sweeping away the fallacious theoretical views which, 

 were at that time in vogue, — particularly the so-called " Humus 

 theory," — and replacing them by a theory of his own, wider in 

 scope, and more conformable with truth. With this, the so-called 

 " Mineral theory," as a general clue for his guidance, Liebig was 

 enabled to thread the labyrinth of intermingled facts and fallacies, 

 which had necessarily resulted from so many investigations, induc- 

 tive and deductive, carried on for so many years, by so many 

 independent thinkers and experimentalists, and recorded in so 

 many scattered memoirs. All of these he was enabled to we gh and 

 appreciate, by the criterion of a new law, or rather system of laws, 

 themselves evolved during his large induction, and established (in 

 a great measure) by help of the very facts they served to elucidate 

 and connect. 



Profiting by the controversial criticism which his book, on its 

 appearance, did not fail to provoke, Liebig made it more perfect 

 in successive editions; and extended it by additional volumes, 

 some modestly entitled " Familiar Letters," some promulgated as 

 codes of Natural Law, but all forming parts of a connected series, 

 in wh ch, as in a mirror, is displayed the progressive development 

 of Liebig's views, in the light of his own and of contemporary 

 researches. By these labors, pursued with unwearied industry 



