Another phase of the change is the greater complexity of the processes of industry. Production becomes technically more complex when interest falls. Rental, product, and present goods, bear a smaller ratio to the value of capital, and therefore it becomes advantageous to apply newly formed capital to uses which before did not justify the investment. Where formerly the utility of a second tool did not justify its making, now it can be made to earn the smaller rental needed to balance its capital value. One form, therefore, which the change takes, is a multiplication of the tools already used. Things are placed wherever most convenient. Another form this change takes is the putting of new links into the chain of technical production. Cost of operation constantly is compared with fixed charges, the interest with the capital investment. Expensive improvements on railroads, the straightening of curves, the tunneling of mountains, the reducing of grades, the replacement of lighter by heavier rails, have been made possible by a fall in the rate of interest. A fall in the rate of interest disturbs the equilibrium that has been arrived at, between the cost of operation, the amount paid for wages, coal, etc., and the income on permanent investment. If the rate of interest has been five per cent. and falls to four per cent. many permanent improvements before unwise become economical. One thousand dollars paid annually in wages then balanced an interest charge on a capital investment of $20,000; now it balances the interest charge on $25,000. It becomes a paying thing for the railroad to abandon or throw aside an enormous capital represented by the old, less perfect roadbed, and build a new one alongside of it. The changes of this kind one sees in traveling on the great and progressive railroads, reflect in part the growth of traffic, but in part also a change of the interest rate, making it a net saving to increase the capital investment in order to reduce the cost of operation per unit of traffic. [Sidenote: Diffused benefits of saving] The benefits of saving viewed broadly are not confined to the owner of the wealth saved, but are diffused throughout society, in the degree that they increase and improve the industrial environment, and thus raise the efficiency of production. Such a change works the same results as would a magical increase in the fertility of the soil, an improvement in the richness and accessibility of natural mineral stores, or in the quantity and quality of artificial appliances. PART II THE VALUE OF HUMAN SERVICES DIVISION A--LABOR AND WAGES CHAPTER 20 LABOR AND CLASSES OF LABORERS § I. RELATION OF LABOR TO WEALTH [Sidenote: Work and play defined and distinguished]