SEC. 2. That any person or persons who shall fire any pistol, gun or rifle, or any other species of fire-arms, within the corporate limits of the city, shall, on conviction thereof before the Police Court, be fined not less than five dollars nor more than fifty dollars: Provided, That all circumstances of necessity may be plead as a defense to the offense described in this section; and, provided further, that the Chief of Police may permit upon the national holidays and other days of public celebration any appropriate display of firearms named in this section.