Section 4
SEC. 4. The proceeds of sales of the lands purchased under the provisions of the Act of Congress of July first, nineteen hundred and two, shall in no case be used for any other purpose than the redemption of the principal of said bonds: Provided, That any other receipts from the said lands shall be first used to pay the interest upon the bonds as it matures, and the surplus, if any, be deposited to the credit of the sinking fund hereby created or the principal of such bonds at their maturity.