The legislature of the proper Territory may provide for the manner in which private lands and possessory claims on the public lands of the United States may be condemned; and where such provision shall not have been made, such condemnation may be made in accordance with section 3 of the act entitled “An Act to amend an Act entitled ‘An Act to aid in the construction of a railroad and telegraph line from the Missouri River to the Pacific Ocean, and to secure to the Government the use of the same for postal, military, and other purposes, approved July 1, 1862,’ ” approved July 2, 1864 [43 U.S.C. 942-3].