13. Whenever the driver of any stage-carriage of the owner of any horse employed in drawing any stage-carriage shall have committed any offence against this Act for the commission where of any penalty is by this Act imposed, other than an offence specified in section 8, and such driver or owner shall not be known, or being known can not be found, or if the penalty cannot be recovered from such driver or owner, the proprietor of such carriage shall be liable to every such penalty as if he had been the driver of such carriage or owner of such horse at the time when such offence was committed:Provided that if any such proprietor shall make out, to the satisfaction of the Magistrate before whom any complaint or information shall be heard, by sufficient evidence, that the offence was committed by such driver or owner without the privity or knowledge of such proprietor, and that no profit, advantage or benefit, either directly or indirectly, has accrued or can accrue to such proprietor therefrom, and that he has used his endeavour to find out such driver or owner, and has done all that was in his power to recover the amount of the penalty from him, the Magistrate may discharge the proprietor from such penalty, and shall levy the same upon such driver or owner when found.