The Secretary of the Interior, under the direction of the President, may use any surplus that may remain in any of the appropriations for the purchase of subsistence for the several Indian tribes, to an amount not exceeding $25,000 in the aggregate, to supply any subsistence deficiency that may occur: Provided, That any diversions which shall be made under authority of this section shall be reported in detail, and the reason therefor, to Congress, at the session of Congress next succeeding such diversion.