Located in a corridor close to the foyer of the Clarendon Laboratory at the University of Oxford, England, the Oxford Electric Bell or Clarendon Dry Pile is an experimental electric bell which has run continuously ever since when it was set up in 1840. It was “one of the first pieces” from a collection of apparatus by clergyman and physicist Robert Walker, and it is surprisingly ringing till to this date, though inaudibly due to being covered under two different layers of clear glass. “The experiment consists of two brass bells, each positioned beneath a dry pile (Dry Pile is a form of battery that could be referred to as the ancestor of the modern dry cell which is used in our cellphone, laptop, etc.), and the pair of piles connected in series.
The clapper is a metal sphere approximately 4 mm in diameter suspended between the piles, which rings the bells alternately due to electrostatic force. As the clapper touches one bell, it is charged by one pile, and then electrostatically repelled, being attracted to the other bell. On hitting the other bell, the process repeats. The use of electrostatic forces means that while high voltage is required to create motion, only a tiny amount of charge is carried from one bell to the other, which is why the piles have been able to last since the apparatus was set up. Its oscillation frequency is 2 hertz.” The exact composition of the dry piles is unknown, but it is known that they have been coated with molten sulphur for insulation and it is thought that they may be Zamboni piles. The Zamboni pile or also referred to as a Duluc Dry Pile is an early electric battery, invented by Giuseppe Zamboni in 1812. It is an “electrostatic battery” and is constructed from discs of silver foil, zinc foil, and paper.
Alternatively, discs of “silver paper” (paper with a thin layer of zinc on one side) gilded on one side or silver paper smeared with manganese oxide and honey might be used. Discs of approximately 20 mm diameter are assembled in stacks, which may be several thousand discs thick, and then either compressed in a glass tube with end caps or stacked between three glass rods with wooden end plates and insulated by dipping in molten sulfur or pitch. At one point this sort of device played an important role in distinguishing between two different theories of electrical action: the theory of contact tension (an obsolete scientific theory based on then-prevailing electrostatic principles) and the theory of chemical action. The Oxford Electric Bell does not demonstrate perpetual motion.
The bell will eventually stop when the dry piles have distributed their charges equally if the clapper does not wear out first. The Bell has produced approximately 10 billion rings since 1840 and holds the Guinness World Record as “the world’s most durable battery ceaseless tintinnabulation”. Apart from occasional short interruptions caused by high humidity, the bell has rung continuously since 1840. The bell may have been constructed in 1825.