252 THE DIRECTION OF MOTION. 



conveyance plus the labour of production is less than the 

 labour of production in the consuming district, transfer 

 commences. Movement in the direction of least resistance 

 is also seen in the establishment of the channels along which 

 intercourse takes place. At the outset, when goods are car- 

 ried on the backs of men and horses, the paths chosen are 

 those which combine shortness with levelness and freedom 

 from obstacles those which are achieved with the smallest 

 exertion. And in the subsequent formation of each high- 

 way, the course taken is that which deviates horizontally 

 from a straight line so far only as is needful to avoid ver- 

 tical deviations entailing greater labour in draught. The 

 smallest total of obstructive forces determines the route, 

 even in seemingly exceptional cases; as where a detour is 

 made to avoid the opposition of a land-owner. All subse- 

 quent improvements, ending in macadamized roads, canals, 

 and railways, which reduce the antagonism of friction and 

 gravity to a minimum, exemplify the same truth. After 

 there comes to be a "choice of roads between one point and 

 another, we still see that the road chosen is that along which 

 the cost of transit is the least: cost being the measure of 

 resistance. Even where, time being a consideration, the 

 more expensive route is followed, it is so because the loss of 

 time involves loss of force. When, division of 



labour having been carried to a considerable extent and 

 means of communication made easy, there arises a marked 

 localization of industries, the relative growths of the popu- 

 lations devoted to them may be interpreted on the same 

 principle. The influx of people to each industrial centre, as 

 well as the rate of multiplication of those already inhabiting 

 it, is determined by the payment for labour; that is by the 

 quantity of commodities which a given amount of effort will 

 obtain. To say that artisans flock to places where, in conse- 

 quence of facilities for production, an extra proportion of 

 produce can be given in the shape of wages; is to say that 

 they flock to places where there are the smallest obstacles to 



