For the purpose of consolidating Federal holdings of land within Gettysburg National Military Park, Pennsylvania, the Secretary of the Interior is authorized, in his discretion, to accept, on behalf of the United States, approximately four acres of non-Federal land within the park boundaries, such land to be conveyed to the United States without cost by the Evergreen Cemetery Association, of Gettysburg. Upon acceptance of title thereto by the United States, such property shall be subject to all laws and regulations applicable to the park. In exchange for the conveyance to the United States of the aforesaid property, the Secretary of the Interior is authorized to convey to the Evergreen Cemetery Association approximately one and one-quarter acres of federally owned land within the park, such property constituting a right-of-way through the Evergreen Cemetery property: Provided, That the aforesaid exchange shall be consummated only upon condition that the Secretary is satisfied that such exchange is in the public interest and that the properties to be exchanged are of approximately equal value.