(3) Where in an enactment it is provided that a person who commits any contravention is liable to a penalty, or commits an offence and, on being convicted, is liable to a fine or by words to that effect, the Court may, where any such order is made, order that the sum adjudged to be paid by the defendant be paid forthwith or within a specified time, and that, in default of such payment, the defendant be imprisoned.