Any private land over which an Indian reservation has been extended by Executive order, may be exchanged at the discretion of the Secretary of the Interior and at the expense of the owner thereof and under such rules and regulations as may be prescribed by the Secretary of the Interior, for vacant, nonmineral, nontimbered, surveyed public lands of equal area and value and situated in the same State or Territory.
(Apr. 21, 1904, ch. 1402, §1,