564 INDUCTION. 



" Now no other explanation," he observes, " of these 

 phenomena can be given, than that a body in the act 

 of combination or decomposition enables another body, 

 with which it is in contact, to enter into the same 

 state." 



Here, 'therefore, is a law of nature of great sim- 

 plicity, but which, owing to the extremely special and 

 limited character of the phenomena in which alone 

 it can be detected experimentally (because in them 

 alone its results are not intermixed and blended with 

 those of other laws), had been very little recognised 

 by chemists, and no one could have ventured, on expe- 

 rimental evidence, to affirm it as a law common to all 

 chemical action; owing to the impossibility of a rigo- 

 rous employment of the Method of Difference where 

 the properties of different kinds of substance are 

 involved, an impossibility which we noticed and cha- 

 racterised in a previous chapter*. Now this extremely 

 special and apparently precarious generalization has, 

 in the hands of Liebig, been converted, by a masterly 

 employment of the Deductive Method, into a law 

 pervading all nature, in the same way as gravitation 

 assumed that character in the hands of Newton ; and 

 has been found to explain, in the most unexpected 

 manner, numerous detached generalizations of a more 

 limited kind, reducing the phenomena concerned in 

 those generalizations into mere cases of itself. 



The contagious influence of chemical action is not a 

 powerful force, and is only capable of overcoming weak 

 affinities : we may, therefore, expect to find it prin- 

 cipally exemplified in the decomposition of substances 

 which are held together by weak chemical forces. 

 Now the force which holds a compound substance 



Supra, p. 484. 



