It shall be the duty of the secretary of internal affairs to ascertain so far as possible the owner or owners of the lands against which liens have been entered under the act of May twentieth, one thousand eight hundred and sixty-four,¹ and its supplements,² and to enforce collection of the amounts of money due the Commonwealth, by reason of the unpaid purchase money, interest and fees due on the lands heretofore sold by the Commonwealth, which now remain unpatented by reason of the unsettled accounts against such lands.