The Secretary of the Interior is authorized to cause to be classified or reclassified and appraised or reappraised, in such manner as he may deem advisable, the unallotted or otherwise unreserved lands within any Indian reservation opened to settlement and entry but not classified and appraised in the manner provided for in the Act or Acts opening such reservations to settlement and entry, or where the existing classification or appraisement is, in the opinion of the Secretary of the Interior, erroneous.