EMPIRICAL LAWS. 49 



uniformity be a law of causation, it is not an ultimate 

 but a derivative law. 



The first sign is, if between the antecedent a and 

 the consequent b there be evidence of some interme- 

 diate link; some phenomenon of which we can col- 

 lect the existence, although from the imperfection of 

 our senses or of our instruments we are unable to 

 ascertain its precise nature and laws. If there be 

 such a phenomenon (which may be denoted by the 

 letter a?), it follows that even if a be the cause of &, it 

 is but the remote cause, and that the law, a causes 6, 

 is resolvable into at least two laws, a causes #', and x 

 causes b. This is a very frequent case, since the 

 operations of nature mostly take place on so minute a 

 scale, that many of the successive steps are either 

 imperceptible, or very indistinctly perceived. 



Take, for example, the laws of the chemical com- 

 position of substances ; as that, hydrogen and oxygen 

 being combined, water is produced. All we see of 

 the process is, that the two gases being mixed in cer- 

 tain proportions, and heat or electricity being applied, 

 an explosion takes place, the gases disappear, and 

 water remains. There is no doubt about the law, or 

 about its being a law of causation. But between the 

 antecedent (the gases in a state of mechanical mix- 

 ture, heated or electrified), and the consequent (the 

 production of water), there must be an intermediate 

 process which we do not see. For if we take any 

 portion whatever of the water, and subject it to 

 analysis, we find that it always contains some hydrogen 

 and some oxygen: nay, the very same proportions of 

 them, namely, two thirds, in volume, of hydrogen, and 

 one third oxygen. This is true of a single drop; it 

 is true of the minutest portion which our instruments 

 are capable of appreciating. Since, then, the smallest 



VOL. II. E 



