The council may make and establish rules for the regulation and government of the police, prescribing and defining the powers and duties of policemen and nightwatchmen, and shall prescribe and enforce such police regulations as will most effectually preserve the peace and good order of the city, preserve the inhabitants from personal violence, and protect public and private property from destruction by fire and from unlawful depredation. The mayor is hereby authorized, whenever he shall deem it necessary for the preservation of peace and good order in the city, to appoint and place on duty such number of temporary policemen as in his judgment the emergencies of the case may require; but such appointments, unless made in accordance with some ordinance or resolution of the council shall not continue longer than 3 days.