In order to carry out the provisions of this chapter the Secretary may accept and utilize such voluntary and uncompensated services of Federal, State, and local officers and employees as are available, and he may appoint and fix the compensation of attorneys, engineers, and experts and he may, subject to the civil-service laws, appoint such other officers and employees as he may find necessary and prescribe their duties. The Secretary is authorized, from sums appropriated pursuant to section 906 of this title, to make such expenditures (including expenditures for personal services; supplies and equipment; lawbooks and books of reference; directories and periodicals; travel expenses; rental at the seat of government and elsewhere; the purchase, operation, or maintenance of passenger-carrying vehicles; and printing and binding) as are appropriate and necessary to carry out the provisions of this chapter.