Ordinances passed as emergency measures shall be subject to referendum in like manner as other ordinances, except that they shall go into effect at the time indicated in such ordinances. If, when submitted to a vote of the electors, an emergency measure be not approved by a majority of those voting thereon, it shall be considered repealed as regards any further action thereunder; but such measure so replaced shall be deemed sufficient authority for payment in accordance with the ordinance, of any expense incurred previous to the referendum vote thereon.