THE INSTABILITY OF THE HOMOGENEOUS. 437 



are made; and for analogous reasons, Hull has become the 

 chief port at which foreign wools are brought in. Even in 

 the establishment of breweries, of dye-works, of slate-quar- 

 ries, of brick-yards, we may see the same truth. So that both 

 in general and in detail, the specializations of the social or- 

 ganism which characterize separate districts, primarily de- 

 pend on local circumstances. Those divisions of labour 

 which under another aspect were interpreted as due to the 

 setting up of motion in the directions of least resistance 

 (§ 80), are here interpreted as due to differences in the in- 

 cident forces; and the two interpretations are quite consist- 

 ent with each other. For that which in each case deter- 

 mines the direction of least resistance, is the distribution of 

 the forces to be overcome; and hence unlikenesses of distri- 

 bution in separate localities, entails unlikenesses in the 

 course of human action in those localities — entails indus- 

 trial differentiations. 



§ 155. It has still to be shown that this general truth is 

 demonstrable a priori. We have to prove specifically that 

 the instability of the homogeneous is a corollary from the 

 persistence of force. Already this has been tacitly implied 

 by assigning unlikeness in the- exposure of its parts to sur- 

 rounding agencies, as the reason why a uniform mass loses 

 its uniformity. But here it will be proper to expand this 

 tacit implication into definite proof. 



On striking a mass of matter with such force as either to 

 indent it or make it fly to pieces, we see both that the blow 

 affects differently its different parts, and that the differences 

 are consequent on the unlike relations of its parts to the 

 force impressed. The part with which the striking body 

 comes in contact, receiving the whole of the communicated 

 momentum, is driven in towards the centre of the mass. 

 It thus compresses and tends to displace the more centrally 

 situated portions of the mass. These, however, cannot be 

 compressed or thrust out of their places without pressing on 



