Sec. 7.
That the board is authorized and directed to investigate and determine as promptly as possible after the enactment of this Act and from time to time thereafter what steamship lines should be established and put in operation from ports in the United States or any Territory, District, or possession thereof to such world and domestic markets as in its judgment are desirable for the promotion, development, expansion, and maintenance of the foreign and coastwise trade of the United States and an adequate postal service, and to determine the type, size, speed, and other requirements of the vessels to be employed upon such lines and the frequency and regularity of their sailings, with a view to furnishing adequate, regular, certain, and permanent service. The board is authorized to sell, and if a satisfactory sale can not be made, to charter such of the vessels referred to in section 4 of this Act or otherwise acquired by the board, as will meet these requirements to responsible persons who are citizens of the United States who agree to establish and maintain such lines upon such terms of payment and other conditions as the board may deem just and necessary to secure and maintain the service desired; and if any such steamship line is deemed desirable and necessary, and if no such citizen can be secured to supply such service by the purchase or charter of vessels on terms satisfactory to the board, the board shall operate vessels on such line until the business is developed so that such vessels may be sold on satisfactory terms and the service maintained, or unless it shall appear within a reasonable time that such line can not be made self-sustaining. The Postmaster General is authorized, notwithstanding the Act entitled "An Act to provide for ocean mail service between the United States and foreign ports, and to promote commerce," approved March 3, 1891, to contract for the carrying of the mails over such lines at such price as may be agreed upon by the board and the Postmaster General: Provided, That preference in the sale or assignment of vessels for operation on such steamship lines shall be given to persons who are citizens of the United States who have the support, financial and otherwise, of the domestic communities primarily interested in such lines if the board is satisfied of the ability of such persons to maintain the service desired and proposed to be maintained, or to persons who are citizens of the United States who may then be maintaining a service from the port of the United States to or in the general direction of the world market port to which the board has determined that such service should be established: Provided further, That where steamship lines and regular service have been established and are being maintained by ships of the board at the time of the enactment of this Act, such lines and service shall be maintained by the board until, in the opinion of the board, the maintenance thereof is unbusinesslike and against the public interests: And provided further, That whenever the board shall determine, as provided in this Act, that trade conditions warrant the establishment of a service or additional service under Government administration where a service is already being given by persons, citizens of the United States, the rates and charges for such Government service shall not be less than the cost thereof, including a proper interest and depreciation charge on the value of Government vessels and equipment employed therein.