DEFINITIONS overbuilt plant and to property held for future use. If the owner has gone too far in the matter of providing capacity or in the matter of securing property not immediately required, the cost of such property may have to be omitted from the rate-base or the rate of return on the rate-base should be lower than would otherwise be allowed. The author suggests that the rate-base determined from the investment, undiminished by accrued depreciation, which he advocates and recommends as the logical basis of the calculation when rates are to be fixed, be called the ‘natural rate-base.” A clear distinction will thereby be made between this rate-base and the other so-called rating bases which involve a consideration of vale, 31