THE DIRECTION OF MOTION. 251 



by catching fish; and hence choose fishing as an occupation. 

 And in places that are rich in coal or metallic ores, the popu- 

 lation, finding that labour devoted to the raising of these 

 materials brings a larger return of food and clothing than 

 when otherwise directed, becomes a population of mi- 

 ners. This last instance introduces us to the phe- 

 nomena of exchange; which equally illustrate the general 

 law. For the practice of barter begins as soon as it facili- 

 tates the fulfilment of men's desires, by diminishing the ex- 

 ertion needed to reach the objects of those desires. When 

 instead of growing his own corn, weaving his own cloth, 

 sewing his own shoes, each man began to confine himself to 

 farming, or weaving, or shoemaking; it was because each 

 found it more laborious to make everything he wanted, 

 than to make a great quantity of one thing and barter the 

 surplus for the rest: by exchange, each procured the neces- 

 saries of life without encountering so much resistance. 

 Moreover, in deciding what commodity to produce, each 

 citizen was, as he is at the present day, guided in the same 

 manner. For besides those local conditions which deter- 

 mine whole sections of a society towards the industries 

 easiest for them, there are also individual conditions and in- 

 dividual aptitudes which to each citizen render certain 

 occupations preferable; and in choosing those forms of ac- 

 tivity which their special circumstances and faculties dic- 

 tate, these social units are severally moving towards the 

 objects of their desires in the directions which present to 

 them the fewest obstacles. The process of transfer 

 which commerce pre-supposes, supplies another series of ex- 

 amples. So long as the forces to be overcome in procuring 

 any necessary of life in the district where it is consumed, 

 are less than the forces to be overcome in procuring it 

 from an adjacent district, exchange does not take place. 

 But when the adjacent district produces it with an economy 

 that is not out-balanced by cost of transit when the dis- 

 tance is so small and the route so easy that the labour of 



