ART OF EGONOMIC DEVELOPMENT 21 on the capital cost. In the case of & large public work, however, whether it be an irrigation canal? s railway, or & hydro-electric power plant, the demand for. its service is necessarily & matter o.f slow growth because no large population can exist m the district without its presence. During the early years of use of the work, therefore, the revenue, after providing for the annual maintenance charge, is not sufficient to pay the interest on the capital. The fact is that it cannot be expected to be so. In p oject estimates an ?rngat?on ?anal is generally allowed ten years for the demand for water to increase sufficientIv return to be realized; in other for the estimated words, the revenue estimate is made on the basis of ten years anticipated grew?h of demand. Railways built through sparsely populated districts may take eve? longer to develope an earning capacity equal to the average current rate of interest on their capital expenditure. In the same way a hydro-electric power station which does not happen to be located beside an existing town or industrial district must necessarily supply current at a loss for several years, whilst manufacturers are discovering the facilities which the locality offers, and are finding the necessary capital and erecting their factories. The return earned by public works of a non-competitive character ?ends con- s?antly to grow, so that after some years the net earnings not only equal the interest on the original and any subsequeut capital outlays, but tenet to exceed it more and more every year owing to the normal growth of population and wealth of the community, and the consequent continually growing increase of demand for its serwces. The point to which it is important that attention should be directed is that what I have outlined is the normal works. experience as regards the earnings of public It must be expected that during the first ten
