law: 15. Tolls.
  4Tolls, according to such rates as are, from time to time, fixed by the State Government, shall be levied on all persons, animals, vehicles and other things crossing any river by a public ferry and not employed or transmitted on the public service:
  Provided that the State Government may, from time to time, declare that any persons, animals, vehicles or other things shall be exempt from payment of such tolls.
  Where the tolls of a ferry have been let under section 8, any such declaration, if made after the date of the 5[lease], shall entitle the lessee to such abatement of the rent payable in respect of the tolls as may be fixed by the Commissioner of the division or such other officer as the State Government may, from time to time, appoint in this behalf by name or in virtue of his office.