196 THE SCIENCE OF LOGIC 



action are all going on at once, each of these causes will produce 

 quantities of heat which will be added together . . . We may 

 call this a case of Iwmogeneous intermixture of effects. &quot; * And it 

 is only to such cases the method of residues can be applied. 

 &quot; There cannot be a simpler case . . . than ascertaining the 

 exact weight of any commodity in a cart, by weighing the cart 

 and load, and then subtracting the tare or weight of the cart 

 alone, which had been previously ascertained.&quot; 2 



The fact has been already emphasized, that it is impossible to regard 

 processes of causation as made up of discontinuous factors (240) ; but we 

 must, if we are to understand them, introduce discontinuity by the mental ab 

 straction involved in analysis. So, when we do isolate them mentally, we 

 must not forget that in the concrete actuality the factors are not independent of 

 one another. It is this mutual interdependence and interference of causes that 

 make inductive research so difficult. When causes &quot; combine &quot; to produce 

 &quot; heteropathic &quot; effects, experiment alone will enable us to detect the nature 

 of the separate influence of each, and the various kinds of effect each will pro 

 duce in combination with others. When causes co-operate by way of simple 

 &quot; composition &quot; to produce &quot; homogeneous &quot; effects, the action of any one 

 &quot; may be (a) augmented, (b} diminished, (c} diverted, (e) wholly counteracted, 

 by that of another cause ; 3 and all these various kinds of interaction may 

 occur at the same time among the effects. Fowler observes truly that in every 

 case each cause produces its appropriate effect, even though it may have dis 

 appeared wholly or partly in the total result. . . . When the full conse 

 quences of a Law are thus affected (modified or neutralised) by other Laws, 

 it is called a tendency.&quot; A &quot; tendency,&quot; therefore, is the action of a causal 

 i nfluence considered as impeded by an opposing causal influence. 



The method of residues is employed extensively, by way of 

 experiment, &quot; in making allowance for the errors or necessary 

 corrections in observations. Few thermometers are quite correct ; 

 but if we put a thermometer into melting snow, which has 

 exactly the temperature of o Centigrade or 32 Fahr., we can 

 observe exactly how much ... we ought to add or subtract 

 from the readings of the thermometer to make them correct &quot;. 4 

 Here the discrepancy between the actual level of the mercury 

 and the point marked o C., or 32 F., may be regarded as a 

 residual phenomenon, whose explanation is to be found in the 

 erroneous graduation of the instrument. 



1 JEVONS, op. cit., p. 252. *ibid. t p. 253. 



3 &quot; Thus, for simple examples we may suppose a body (a) pulled by two forces in 

 exactly the same direction ; (b) pulled by two forces of different magnitudes in 

 exactly opposite directions; (c) pulled in one direction by one force, and by an 

 other force pulled in a direction at right angles to the former ; (rf) pulled by two 

 equal forces in exactly opposite directions, when no motion takes place &quot;. &amp;lt;MELLONE, 

 op. cit., p. 317, n. 



4 JEVONS, op. cit., p. 253. 



