Upon execution and filing with the Secretary of the Interior, by the Northern Pacific Railroad Company, of proper deed releasing and conveying to the United States the lands in Mount Rainier National Park, also the lands in the Pacific National Forest which have been heretofore granted by the United States to said company, whether surveyed or unsurveyed, and which lie opposite said company's constructed road, said company is authorized to select an equal quantity of nonmineral public lands, so classified as nonmineral at the time of actual Government survey, which has been or shall be made, of the United States not reserved and to which no adverse right or claim shall have attached or have been initiated at the time of the making of such selection, lying within any State into or through which the railroad of said Northern Pacific Railroad Company runs, to the extent of the lands so relinquished and released to the United States. Any settlers on lands in said national park may relinquish their rights thereto and take other public lands in lieu thereof, to the same extent and under the same limitations and conditions as are provided by law for national forests and national parks.