520 INDUCTION. 



sensation ; that is, not the cause, properly speaking, but the 

 cause of the cause ; the real cause of the sensation is the 

 change in the state of the nerve. Future experience may not 

 only give us more knowledge than we now have of the parti- 

 cular nature of this change, but may also interpolate another 

 link : between the contact (for example) of the object with our 

 outward organs, and the production of the change of state in 

 the nerve, there may take place some electric phenomenon ; 

 or some phenomenon of a nature not resembling the effects of 

 any known agency. Hitherto, however, no such intermediate 

 link has been discovered; and the touch of the object must 

 be considered, provisionally, as the proximate cause of the 

 affection of the nerve. The sequence, therefore, of a sensation 

 of touch on contact with an object, is ascertained not to be 

 an ultimate law ; it is resolved, as the phrase is, into two other 

 laws, the law, that contact with an object produces an affec- 

 tion of the nerve ; and the law, that an affection of the nerve 

 produces sensation. 



To take another example : the more powerful acids corrode 

 or blacken organic compounds. This is a case of causation, 

 but of remote causation ; and is said to be explained when it 

 is shown that there is an intermediate link, namely, the separa- 

 tion of some of the chemical elements of the organic structure 

 from the rest, and their entering into combination with the 

 acid. The acid causes this separation of the elements, and the 

 separation of the elements causes the disorganization, and often 

 the charring of the structure. So, again, chlorine extracts 

 colouring matters, (whence its efficacy in bleaching,) and 

 purifies the air from infection. This law is resolved into the 

 two following laws. Chlorine has a powerful affinity for bases 

 of all kinds, particularly metallic bases and hydrogen. Such 

 bases are essential elements of colouring matters and conta- 

 gious compounds : which substances, therefore, are decomposed 

 and destroyed by chlorine. 



4. It is of importance to remark, that when a sequence 

 of phenomena is thus resolved into other laws, they are always 

 laws more general than itself. The law that A is followed by 



