IN GEOMETRIC TERMS

lines depicted in Chart 34. Supply and demand curvescan equally well be derived from the M line, the 0 lineand the W lines shown in Chart 38. A series of positionsof PQ, with different slopes, gives us all the materialneeded, each slope giving a rate of interest and eachhorizontal spread between P and Q being the demand forloans (if Q is east of P) or supply of loans (if Q is westof P). The only difference is that P is not now fixed as inthe first approximation, but shifts as PQ has differentslopes.

It will be noted that the Opportunity line which em-bodies the technical or production elements in the prob-lem has no more relation to the supply than to thedemand, although this runs counter to the commonnotions that productivity rules one side of the market andtime preference the other.

It will also be noted that the map gives us vastly morelight on the analysis of interest than do the mere supplyand demand curves. But even the map fails to give acomplete picture because, in particular, it shows onlytwo years. The truth seems to be that no complete visu-alization of this difficult problem is possible. The onlycomplete symbolization which seems to be possible is interms of mathematical formulas as in the next twochapters.

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