That all lands granted in quantity or as indemnity by this act shall be selected, under the direction of the secretary of the interior, from the surveyed, unreserved, and unappropriated public lands of the United States within the limits of the respective states entitled thereto. And there shall be deducted from the number of acres of land donated by this act for specific objects to said states the number of acres in each heretofore donated by Congress to said territories for similar objects.