Mystery Object

Went to a friends house today for our reading/ writing group.
Among the many interesting objects in her house was this.

Barlow's Wheel 
English mathematician Peter Barlow devised an instrument in 1822 that built on advances from earlier in the century, including the invention of the battery, to create a very early kind of electric motor.
What came to be known as Barlow’s wheel combined the powers of electricity and magnetism to produce continuous motion.
The metal wheel is connected in a circuit with a battery and a pool of mercury, The wheel can be raised out of the mercury to break the circuit, or lowered into the mercury to complete the circuit.
When the circuit is complete, a horseshoe magnet positioned around the wheel provides a magnetic field that interacts with the magnetic field created by the electric current, making the wheel move.
Barlow’s wheel was one of the first machines to harness the interplay between electric and magnetic forces that had been discovered just two years earlier by Hans Christian Ørsted.
It shows how an electrical current generating around it a circular magnetic field can interact with a second magnetic field to produce force and motion.
Jacqui recognised this and said they used to have one in the school’s  lab as a period piece but they are now banned because of the mercury.