542 TRANSACTIONS OF SECTION’ F. 
quarter at a given epoch, and OM the quantity produced in a standard time! 
For if more than OM were grown it could only be sold at a loss; if less the grow- 
ing of corn would produce an abnormal profit, which would soon cause an expan- 
sion, so as to bring the quantity grown and sold up to the maximum that could 
be profitably produced. 
These diagrams have therefore done more than present a state of facts; 
they have solved a problem, just as could be done by a pair of algebraic 
equations, ; 
Moreover, other illustrations can be derived from fig. 5.: By drawing the 
series of lines shown in fig. 6 meanings can be given to various parts of the 
¥ 
O M xX i 
Fic. 6. 
diagram. The area NPMO represents the total price paid for the corn; the 
area APMO represents the total cost of growing; the area APN, which is 
the difference between them, represents the surplus profit obtained from the use 
of the better lands, or, in other words, rent; the area BPMO represents the 
total enjoyment the consumer derives from the corn; expressed in terms of 
money; and since NPMO is the price he pays for it, BNP is the surplus 
enjoyment he gets by obtaining corn for less than he would have given for it 
had there been a famine. 
Let us go a little further. Suppose that a tax were laid on corn, and that all 
corn grown in a country were subject to an excise duty like that now levied on 
the manufacture of spirits. Suppose the duty were 5s. a quarter, and, to simplify 
fe) M M x 
Ere. 7. 
the problem, suppose no corn came in from the outside. Then the curve APS 
(fig. 7) would be pushed upwards all along its length by 5s., and assume a 
position A’P’S’. And notice that the price would rise not by 5s., but by some 
amount rather less than 5s. For M’P/—MP must always be less than the upward 
movement of the curve APS. Again, the rent would be decreased, for the area 
N’P’A’ is less than NPA. The amount grown would decrease from’ OM to 
OM’. The proceeds of the tax would be OM’ times five shillings, and the 
consumers’: surplus of enjoyment would have considerably diminished. This 
is all obvious enough if you look at the curves. But I want to ask whether, 
