(3.iv.2) There is another circumstance, which very obviously affords a motive to exchangecommodities. Some can be produced only in particular places. Metals, coals, and various othercommodities of the greatest importance, are the product of certain spots. The same is the casewith some vegetable productions, to which every soil and climate are not adapted. Certaincommodities, though not confined to particular spots, can yet be more conveniently and cheaplyproduced in some places than in others; commodities, for example, which require a greatconsumption of fuel, in a coal country; commodities, the manufacture of which requires a strongmoving power, where a sufficient fall of water can be obtained; commodities which require anextraordinary proportion of manual labour, where provisions, and consequently labour, arecheap.
(3.iv.3) These are all obvious causes. There is another cause, which requires rather moreexplanation. If two countries can both of them produce two commodities, corn, for example, andcloth, but not both commodities, with the same comparative facility, the two countries will findtheir advantage in confining themselves, each to one of the commodities, bartering for the other.
If one of the countries can produce one of the commodities with peculiar advantages, and theother the other with peculiar advantages, the motive is immediately apparent which shouldinduce each to confine itself to the commodity which it has peculiar advantages for producing.
But the motive may no less exist, where one of the two countries has facilities superior to theother in producing both commodities.
(3.iv.4) By superior facilities, I mean, the power of producing the same effect with lesslabour.
The conclusion, too, will be the same, whether we suppose the labour to be more or less highlypaid. Suppose that Poland can produce corn and cloth with less labour than England, it will notfollow that it may not be the interest of Poland to import one of the commodities from England.
If the degree, in which it can produce with less labour, is the same in both cases; if, forexample, the same quantity of corn and cloth which Poland can produce, each with 100 days' labour, requires each 150 days' labour in England, Poland will have no motive to import eitherfrom England. But if, at the same time that the quantity of cloth, which, in Poland, is producedwith 100 days' labour, can be produced in England with 150 days' labour; the corn, which isproduced in Poland with 100 days' labour, requires 200 days' labour in England; in that case, itwill be the interest of Poland to import her cloth from England. The evidence of thesepropositions may thus be traced.
(3.iv.5) If the cloth and the corn, each of which required 100 days' labour in Poland, requiredeach 150 days' labour in England, it would follow, that the cloth of 150 days' labour in England,if sent to Poland, would be equal to the cloth of 100 days' labour in Poland: if exchanged forcorn, therefore, it would exchange for the corn of only 100 days' labour. But the corn of 100days' labour in Poland was supposed to be the same quantity with that of 150 days' labour inEngland. With 150 days' labour in cloth, therefore, England would only get as much corn inPoland as she could raise with 150 days' labour at home; and she would, on importing it, havethe cost of carriage besides. In these circumstances no exchange would take place.
(3.iv.6) If, on the other hand, while the cloth produced with 100 days' labour in Poland wasproduced with 150 days' labour in England, the corn which was produced in Poland with 100days' labour could not be produced in England with less than 200 days' labour; an adequatemotive to exchange would immediately arise. With a quantity of cloth which England producedwith 150 days' labour, she would be able to purchase as much corn in Poland as was thereproduced with 100 days' labour; but the quantity, which was there produced with 100 days' labour, would be as great as the quantity produced in England with 200 days' labour. If theexchange, however, was made in this manner, the whole of the advantage would be on the partof England; and Poland would gain nothing, paying as much for the cloth she received fromEngland, as the cost of producing it for herself.
(3.iv.7) But the power of Poland would be reciprocal. With a quantity of corn which cost her100 days' labour, equal to the quantity produced in England by 200 days' labour, she could in thesupposed case purchase, in England, the produce of 200 days' labour in cloth. The produce of150 days' labour in England in the article of cloth would be equal to the produce of 100 days' labour in Poland. If, with the produce of 100 days' labour, she could purchase, not the produce of150, but the produce of 200, she also would obtain the whole of the advantage, and Englandwould purchase corn, which she could produce by 200 days' labour, with the product of as manydays' labour in other commodities. The result of competition would be to divide the advantageequally between them.
