Section 473, act Dec. 5, 1924, ch. 4, 4, subsec. F, 43 Stat. 702, related to payment of project construction charges in installments after Dec. 5, 1924. Section 474, act Dec. 5, 1924, ch. 4, 4, subsec. F, 43 Stat. 702, related to modification of contracts existing prior to Dec. 5, 1924, in respect to payment of construction charges.