250 THE DIRECTION OF MOTION. 



added the allied one daily furnished by emigration; which 

 we see going on towards countries presenting the fewest ob- 

 stacles to the self-preservation of individuals, and therefore 

 to national growth. Similarly with that resistance 



to the movements of a society which neighbouring societies 

 offer. Each of the tribes or nations inhabiting any region, 

 increases in numbers until it outgrows its means of subsist- 

 ence. In each there is thus a force ever pressing outwards 

 on to adjacent areas a force antagonized by like forces in 

 the tribes or nations occupying those areas. And the ever- 

 recurring wars that result the conquests of weaker tribes 

 or nations, and the over-running of their territories by the 

 victors, are instances of social movements taking place in 

 the directions of least resistance. Nor do the conquered 

 peoples, when they escape extermination or enslavement, 

 fail to show us movements that are similarly determined. 

 For migrating as they do to less fertile regions taking ref- 

 uge in deserts or among mountains moving in a direction 

 where the resistance to social growth is comparatively great; 

 they still do this only under an excess of pressure in all other 

 directions: the physical obstacles to self-preservation they 

 encounter, being really less than the obstacles offered by 

 the enemies from whom they fly. 



Internal social movements may also be thus interpreted. 

 Localities naturally fitted for producing particular com- 

 modities that is, localities in which such commodities are 

 got at the least cost of force that is, localities in which the 

 desires for these commodities meet with the least resistance ; 

 become localities especially devoted to the obtainment of 

 these commodities. Where soil and climate render wheat a 

 profitable crop, or a crop from which the greatest amount 

 of life-sustaining power is gained by a given quantity of 

 effort, the growth of wheat becomes the dominant industry. 

 Where wheat cannot be economically produced, oats, or 

 rye, or maize, or rice, or potatoes, is the agricultural staple. 

 Along sea-shores men support themselves with least effort 



