WAGES, PROFITS AND INTEREST 175 
provisionally assume that all the land is equally 
valuable in respect of fertility and situation. 
If the population is so dense that the whole 
of the land is in use, the land will have a 
marginal worth per acre equal to the difference 
that would be made to the product by the 
removal of one acre. If, however, the popula 
tion is such that the whole of the land is not 
occupied, land will have no marginal worth, 
because, like air, there is more than enough 
of it. It is premised, of course, that the 
land is not monopolised. When land is not 
monopolised, its value is governed by the 
marginal worth of different quantities of land 
in relation to what the fixed supply is. 
The supply of labour will engage our atten 
tion next. Here we discover more complex 
conditions. The size of the population is 
certainly dependent in some degree upon 
earnings—other things being equal it may not 
infrequently happen that population rises 
as earnings rise—but the laws of population 
are so obscure that all sweeping and dogmatic 
pronouncements must be viewed with 
suspicion. What is perfectly certain, however, 
is that the relative wages paid in many or 
most trades settle the supply of labour 
offered in those trades. Were the wages 
of carpenters to rise, other wages remaining