392 



SCIENTIFIC THOUGHT. 



marks an epoch equally in the science of organic chemistry 

 proper and in the life-work of Liebig. The necessity 

 of collecting and systematising the scattered labours 

 of chemists and physiologists in this department was 

 simultaneously felt in France, where Liebig's friend and 

 rival, Dumas, published his ' Essai de Statique chimique 

 des ^tres organises ' as a conclusion to his course of 



Liebig broke through the barriers 

 which in his age separated science 

 in Germany from general culture, 

 and the university professor from 

 the man of the world. From France 

 he learnt the merit of a clear style, 

 and from England the higher art of 

 popularisation. His fame did not 

 grow slowly and surely like that of 

 Helmholtz, spreading almost imper- 

 ceptibly from narrower into ever 

 wider circles : he took the world 

 by surprise, and stirred up every- 

 where inquiry, opposition, and con- 

 troversy. He ventured on great 

 and sweeping generalisations and on 

 daring experiments and prophecies, 

 with the result that in the final 

 establishment of truth his oppon- 

 ents had frequently as great a share 

 as himself. Notable instances are 

 his so - called " mineral theory " 

 of manuring and his theory of fer- 

 mentation. Through the former 

 the great division which separated 

 the processes in the living from 

 those which obtained in the inani- 

 mate (mineral) world was broken 

 down ; and through the latter the 

 modern notions of the ubiquity and 

 continuity of life were to a large 

 extent established, as will be seen 

 in the sequel of this chapter. The 

 correct notions which he enter- 

 tained as to the necessity of the 

 mineral ingredients (phosphoric 

 acid, lime, potash, &c.) in plant- 

 manures, which he started in op- 

 position to the older " humus " or 

 " vegetable mould " theory, was on 

 the point of being refuted by his 



insistence on making his chemical 

 fertilisers insoluble, ignorant as he 

 then was of the absorbing and re- 

 taining function of mould ; but, a 

 generation after, the prevailing pre- 

 dilection for soluble manures was 

 again much modified by the intro- 

 duction of the " Thomas slag," and 

 the enormous improvements in the 

 process of extreme pulverisation. 

 Prof. Vogel in his above-mentioned 

 address gives many extracts from 

 Liebig's writings, referring to the 

 final and corrected expression of 

 the chemical theory of fertilisation. 

 These are so characteristic of 

 Liebig's habit of thought and his 

 whole mental attitude, that I tran- 

 scribe them: "When I knew the 

 reason why my fertilisers would not 

 act, I felt like a man who had re- 

 ceived a new life, for through this 

 all processes of agriculture were 

 explained, and now that the law 

 is known and lies clearly before 

 our eyes, there remains only the 

 wonder that we did not see it long 

 ago : but the human mind is a 

 queer thing, — what does not fit into 

 the circle of ideas once given, does 

 not exist for it. ... I had sinned 

 against the wisdom of the Creator, 

 and for this had received merited 

 punishment. I wanted to improve 

 His work, and in my blindness I 

 thought that in the wonderful 

 chain of laws which bind life to 

 the surface of the earth, one link 

 was missing which I, a helpless 

 worm, could supply" {loc. cit., p. 

 34). 



