46 INDUCTION. 



particles of which must have been in the blood, but which 

 differ from it most widely both in mechanical properties and 

 in chemical composition. Here, then, are abundance of un- 

 known links to be filled up ; and there can be no doubt that 

 the laws of the phenomena of vegetative or organic life are 

 derivative laws, dependent on properties of the corpuscles, and 

 of those elementary tissues which are comparatively simple 

 combinations of corpuscles. 



The first sign, then, from which a law of causation, though 

 hitherto unresolved, may be inferred to be a derivative law, 

 is any indication of the existence of an intermediate link or 

 links between the antecedent and the consequent. The 

 second is, when the antecedent is an extremely complex 

 phenomenon, and its effects therefore, probably, in part at 

 least, compounded of the effects of its different elements ; 

 since we know that the case in which the effect of the whole 

 is not made up of the effects of its parts, is exceptional, 

 the Composition of Causes being by far the more ordinary 

 case. 



We will illustrate this by two examples, in one of which 

 the antecedent is the sum of many homogeneous, in the other 

 of heterogeneous, parts. The weight of a body is made up 

 of the weights of its minute particles : a truth which astro- 

 nomers express in its most general terms, when they say that 

 bodies, at equal distances, gravitate to one another in propor- 

 tion to their quantity of matter. All true propositions, 

 therefore, which can be made concerning gravity, are deriva- 

 tive laws ; the ultimate law into which they are all resolvable 

 being, that every particle of matter attracts every other. As 

 our second example, we may take any of the sequences ob- 

 served in meteorology : for instance, a diminution of the pres- 

 sure of the atmosphere (indicated by a fall of the barometer) 

 is followed by rain... The antecedent is here a complex 

 phenomenon, made up of heterogeneous elements ; the column 

 of the atmosphere over any particular place consisting of two 

 parts, a column of air, and a column of aqueous vapour mixed 

 with it; and the change in the two together manifested by a 

 fall of the barometer, and followed by rain, must be either a 



