Sec. 23.
That the owner of a vessel documented under the laws of the United States and operated in foreign trade shall, for each of the ten taxable years while so operated, beginning with the first taxable year ending after the enactment of this Act, be allowed as a deduction for the purpose of ascertaining his net income subject to the war-profits and excess-profits taxes imposed by Title III of the Revenue Act of 1918 an amount equivalent to the net earnings of such vessel during such taxable year, determined in accordance with rules and regulations to be made by the board: Provided, That such owner shall not be entitled to such deduction unless during such taxable year he invested, or set aside under rules and regulations to be made by the board in a trust fund for investment, in the building in shipyards in the United States of new vessels of a type and kind approved by the board, an amount, to be determined by the Secretary of the Treasury and certified by him to the board, equivalent to the war-profits and excess-profits taxes that would have been payable by such owner on account of the net earnings of such vessels but for the deduction allowed under the provisions of this section: Provided further, That at least two-thirds of the cost of any vessel constructed under this paragraph shall be paid for out of the ordinary funds or capital of the person having such vessel constructed.
That during the period of ten years from the enactment of this Act any person a citizen of the United States who may sell a vessel documented under the laws of the United States and built prior to January 1, 1914, shall be exempt from all income taxes that would be payable upon any of the proceeds of such sale under Title I, Title II, and Title III of the Revenue Act of 1918 if the entire proceeds thereof shall be invested in the building of new ships in American shipyards, such ships to be documented under the laws of the United States and to be of a type approved by the board.