ART OF Ei?ONOMI(? DEVELOPMENT 81 o! capital outlay to the percentage saving of time which is just remunerative--will be found to increase with the following conditions: .. (1) the higher the rate o? interest to be paid on borrowed capital. (2) the larger the total amount o! capital kept lying idle in connected works relatively to the capital outlay on the work itself. (?) the greater the estimated earning capacity on maturity of the work as a whole, or o! the series o! works kept idle. In public works where benefit of the population and indirect revenue due to increase of taxes are objects o! policy, the earlier accrual of these forms of income is a factor which should be These considerable advantages given its full weight. ? which may be expected to result from every successful public work should not be omitted'from account merely because o! the difiioulty of obtaining s nllmerioally precise estimate o! what they are likely to amount to. Even if these factors be given s very moderate estimate in terms of money income, it will be makes an impotent found often that their inclusion difference in the solution of the problem o! the most economical speed of construction. The principle I have explained of avoiding loss of interest by delay in carrying out a difficult part of any work may be expanded into a general theory of the correc? timing o! every operation connected with the expenditure o! money on engineering works, and as a useful study for engineers I may recommend the graphic method of solving this problem described by (?. L. Bennet in his article entitled "A method of determining the time of pedorman?e o! work, with special application to grading", and published in Engine?ing and Contra?ting, May 1?, 1914, pp. 555-7. I S?,e postre, Chsp. IV f, II, 12,
