64 INDUCTION. 



of a connexion between the two phenomena remains 

 an empirical law. 



3. Having considered in what manner it may be 

 determined whether any given conjunction of pheno- 

 mena is casual or the result of some law ; to complete 

 the theory of chance, it is necessary that we should 

 now consider those effects which are partly the result 

 of chance and partly of law : or in other words, in 

 which the effects of casual conjunctions of causes are 

 habitually blended in one result with the effects of a 

 constant cause. 



This is a case of Composition of Causes ; and the 

 peculiarity of it is, that instead of two or more causes 

 intermixing their effects in a regular manner with 

 those of one another, we have now one constant cause, 

 producing an effect which is successively modified 

 by a series of variable causes. Thus, as summer 

 advances, the approach of the sun to a vertical posi- 

 tion tends to produce a constant increase of tempera- 

 ture ; but with this effect of a constant cause, there are 

 blended the effects of many variable causes, winds, 

 clouds, evaporation, electric agencies and the like, so 

 that the temperature on any given day depends in 

 part upon these fleeting causes, and only in part upon 

 the constant cause. If the effect of the constant 

 cause is always accompanied and disguised by effects 

 of variable causes, it is impossible to ascertain the law 

 of the constant cause in the ordinary manner, by sepa- 

 rating it from all other causes and observing it apart. 

 Hence arises the necessity of an additional rule of 

 experimental inquiry. 



When the action of a cause A is liable to be inter- 

 fered with, not steadily by the same cause or causes, 

 but by different causes at different times, and when 



