It shall be the duty of the secretary of the land office, on the settlement of any account for moneys due on lands, other than those due on mortgage or lien, within any part of this commonwealth, except such lands as are situate north and west of the rivers Ohio and Allegheny and Conewango creek, to ascertain the amount of the principal and interest due at the time of passing this act, upon such account, and upon the aggregate amount so found due it shall be his duty to charge interest until the amount of the account shall have been discharged.
64 P.S. § 418