 As a result, many fire departments provide traditional helmets using modern plastic and composite helmets without eagles or beavers, jokingly referred to as "salad bowls", "turtle shells" and "slick tops" due to their streamlined shape.However, many firefighters and fire departments still retain the leather helmet as a matter of tradition.In 1871, British physicist John Tyndall wrote about his new invention, a "fireman's respirator", featuring a valve chamber and filter tube.