If any person summoned to appear before a magistrate to answer a charge of an offence against this Act or any rule, regulation or bye-law made thereunder fails to appear at the time and place mentioned in the summons, or on any date to which the hearing of the case is adjourned, the magistrate may hear and determine the case in his absence, if--
         (a) service of the summons is proved to his satisfaction, and
         (b) no sufficient cause is shown, for the non-appearance of such person.