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ment for the agents in production other than 
land will, therefore, be obtained from the 
proceeds of a quantity of produce represented 
by the marginal returns, multiplied by the 
number of doses applied. When there is a 
surplus produce (that is produce over and 
above this amount) its value is rent. 
The point will have been seized already, no 
doubt, that, in order to bring in the element of 
situational convenience, the doses of labour 
and capital must be made to cover the cost of 
carrying the factors in production to the land 
and produce to the market. For the sake 
of simplicity we are leaving out specific 
mention of these costs, and for the same 
reason we are positing that the produce is 
all of one kind. It may be remarked, how 
ever, that when the produce is of many kinds 
we have a common denominator for its 
measurement in its value ; and that the 
principle of substitution, which naturally 
settles how much of one kind of produce is 
produced and how much of another, will 
bring it about that the proportion of the 
different kinds of produce will be such that, 
in view of the price of each, the value of the 
total output of the land is maximised. 
Let me illustrate our simplified case with 
figures relating to a given piece of land :— “