SOME DOCTRINES OF POLITICAL ECONOMY. 149 



view, at least for the mathematical reader, than in the numerical way. It has been seen, for 

 instance, (57), that if there be a trade between any two countries, say Poland and England, 

 Poland exporting, we will suppose, corn, and England, cloth, the case in which the trade is advan- 

 tageous to both countries is (on the suppositions made) confined within narrow limits, namely, 

 when the mutual demand is very nearly equal : and that if the demand of Poland for our 

 commodity, cloth, be much smaller than our demand for theirs, corn, the advantage, according 

 to the mathematical principles here applied, rests entirely with Poland. 



67. But there is another consideration to be attended to. All the principles here applied 

 are principles of equilibrium : that is, principles depending on the assumption of an enduring 

 state of equality on the two sides : such are the principles of uniformity of international 

 prices (36), the equality of import and export (37), transferable capital (44). These principles 

 are each expressed by an equation, which enters into the investigation. But in fact, we never 

 can have an absolute equilibrium. Even if the principles just mentioned be true, they exist 

 as tendencies only, not as conditions attained : just as the principle that water finds its level 

 governs the state of fluids, (rivers and oceans) not by producing equilibrium, but by producing 

 motion, the level never being attained. The equilibrium theory of the tides is highly imperfect, 

 and in many respects erroneous : the equilibrium theory of trade is probably no less so. Yet 

 the equilibrium theory of the tides has been very useful in suggesting the form and laws of 

 many of the principal features of tidal phenomena ; though it is absolutely necessary to obtain 

 the amount and epoch of the inequalities by local observations. It is possible that, in like 

 manner, the equilibrium theory of trade may suggest propositions respecting the natural 

 progress of trade, which propositions may be afterwards confirmed, limited, and reduced to 

 their due measure by experience. 



Trinity College, 



April 3, 1850. 



