Nathan H. Fogg, Boston, Mass.--When the car is suspended normally from
the rope, the rubber balls, arranged in sockets near the lower part of
the car, are supported on their seats in a state of rest; but the
instant that the rope breaks or gets detached from the bolt the action
of a spiral spring throws an actuating plate downward, and levers and
ball-carrying rods upward. The balls are thus thrown off their seats
and wedged between the inclined sides of the pockets and the guide
posts of the elevator so as to stop thereby the car.