Section 10. Any person convicted of an offence under section nine, after having been previously convicted of an

10. Any person convicted of an offence under section nine, after having been previously convicted of an offence under that section or section 11 of the Inland Customs Act, 1875, or under any enactment repealed by that Act, shall be punished with imprisonment for a term which may extend to six months, in addition to the punishment which may be inflicted for a first offence under section nine; and every such person shall, upon every subsequent conviction of an offence under section nine, be liable to imprisonment for a term which may extend to six months, in addition to any term of imprisonment to which he was liable at his last previous conviction.