The mayor, or in his absence the president or vice-president of the council, shall call the meeting to order at the hour designated for the meeting. If a quorum is not present, the recorder shall immediately inform the absent members, except those known to be unavoidably detained, that their presence is required to enable the council to proceed. If the absent member or members do not appear after the notice, the members present shall adjourn until a specific time or until the next regular meeting.