Rev. St. U. S. c. 6, sec. 2318 et seq. [U. S. Comp. St 1901, p. 1423], provides for the acquisition of title to unappropriated mineral lands belonging to the United States, and sets forth at considerable length the mode of procedure in acquiring such title. These chapters, which, as amended in 1891, embody the law that was in force in 1899 and thereafter, during which time the proceedings were had in regard to this land, intrust the disposal of both classes of lands to the land department and provide that the Issues of fact that arise In all cases in regard to the patenting of agricultural or mineral lands, whether In a contest between different claimants for agricultural lands, or between different claimants for mineral lands, or In a contest between claimants for the same tract of land, in which one party may claim as agricultural, and the other as mineral, any public land of the United States, shall be submitted to the determination of the proper officials of the land department Their findings on all issues of fact In cases thus submitted to them for determination are made conclusive the same as judgments of courts of record, and can only be collaterally attacked when invalid by reason of fraud In their procurement Wilcox v. McConnell, 13 Pet (U. S.) 511, 10 L. Ed. 264; Barnard's Heirs v. Ashley's Heirs et al. 18 How. (U. S.) 44, 15 L. Ed. 285; Lytle et al. v. State of Arkansas, 9 How. (U. S.) 332, 13 L. Ed. 153; Johnson v. Towsley, 13 Wall. (U. S.) 72, 20 L. Ed. 485; Warren v. Van Brunt 19 Wall. (U. S.) 053, 22 L. Ed. 219; Shepley et al. v. Cowan et al. 91 U. S. 340, 23 L. Ed. 424; Moore v. Robbins, 96 U. S. 535, 24 L. Ed. 848; Heath v. Wallace, 138 U. S. 573, 11 Sup. Ct. 380, 34 I* Ed. 1063. There have been cited as exceptions to this rule cases in which patents have been issued for lands that had been previously disposed of, and were therefore not, at the date of patent, unappropriated public lands of the United States, and cases In which land patented under certain laws had been theretofore, by act of Congress, specially reserved or exempted from patent under such laws, and therefore the patents Issued by the land department had been, In these instances, held to be void as being in excess of its jurisdiction.