Mysterious bell that won't stop ringing...
There is an experiment running in the Clarendon Laboratory at Oxford University, which has been running continuously since it was set up in 1840. It's a pair bells rung by a small hanging brass ball - and it's been ringing continuously for over 176 years!
The device, technically catalogued as the Clarendon Dry Pile, is known around the world (of nerds) as the Oxford Electric Bell. It was created during a time of much debate about the causes of electricity in the material world. The experiment, which includes a pair of mysterious sulphur encased batteries, ultimately played a roll in supporting the chemical-action hypothesis as to why batteries work. (Here's an interesting video on the history around the voltaic pile if you're interested in more about that.)
The experiment currently sits under a protective glass jar and can be seen but not heard. The tiny metal clapper hanging from a string makes its cycle from one bell to the other and back at a rate of about two times per second. Rather than being pushed and pulled by electromagnetic force, the clapper is alternately driven from one bell to the other by electrostatic forces, which is actually pretty interesting!
Static forces: As the clapper makes contact with one bell, say the positively charged one, it takes on a positive charge. It is repelled (alike charges repel) and attracted to the negatively charged bell. Once it strikes the negatively charged bell, the situation is reversed, and the bell makes an about face... And so it has gone for the better part of two centuries!
Something else noteworthy about this static electric bell-wringing technique: It was first perfected by none-other than Benjamin Franklin during his bout with meteorology in the 1750s. Check out Franklin Bells.
The process of ringing the bells requires a very minuscule amount of current, on the order of around one nanoamp say researchers say. The batteries consist of two stacks of metal disks of unknown composition, dipped in protective sulphur. When originally set up, the batteries produced around 2000 volts of potential between the bells. The power requirements are quite low, but the longevity has proven to be surprising. Apparently physicist Robert Walker only expected the apparatus to function for a few months when he originally set it up in 1840.
Here are some interesting videos on the Oxford Electric Bells, pulled from YouTube for your wonder and delight: