large genus.' The 'inherent properties of land,' which 'include,' and often chiefly consist of, 'the space relations of the plot in question, and the annuity that nature has given it of sunlight and air and rain,' are a 'typical instance' of the class; for, like 'other gifts from the bounty of nature,' they 'are incapable of increase by man's efforts in any period of time however long.' But the permanent improvements usually made by an English landlord, although incurred in the first instance with the expectation of an adequate return, when once incorporated with the soil, must also 'be taken for granted' over shorter periods of time, and the 'income derived' from them 'may be regarded as a Quasi-Rent.' And thus by a 'continuous series' we may pass to 'less permanent improvements, to farm and factory buildings, to steam engines, &c., and finally to the less durable and less slowly-made implements. And parallel to the series of the material agents of production there is a similar series of human abilities, those that are the free gifts of nature and those that are the result of a more or less long and specialized process of training.'
The continuity of this series does not, it is true, determine the question of the origin of the differential advantages to which it relates; and Professor Marshall is very careful to indicate the dangers of pushing the analogy of rent too far, and to emphasise its intimate reference to the periods of time which we have in view. But it does seem to be legitimate to argue from these and similar considerations to the improbability of an abrupt distinction as we pass from rent in the 'strict sense' to rent popularly so called, and to infer from the more apparent difficulty of distinguishing between what is earned and what is unearned in the case of these other differential advantages to a likelihood, at least, of difficulty in the case of land. A farmer, in making his present contract for rent, does not concern himself with the past history of the causes of the fertility or situation of the land, but with its present advantages, and he makes no attempt to draw the distinction between the earned and the unearned. And, in the future, he and his landlord may allow the nominal rent to remain unaltered in spite of increased prosperity or intensified depression in agriculture, in consideration simply of lessened expenditure or added liberality in the matter of improvements. Ricardo, again, himself declares that 'there is not a manufacture in which nature does not give assistance to man;' and opportunity and chance and society, with its changing demands and altering organisation, play no inconsiderable part in the determination of professional incomes and the earnings of
