When the circuit of the wire, mercury, and battery was completed, the wire began rotating around the magnet.
(the circuit of the wire, mercury, and battery; was completed; ) (the wire; began; T:When the circuit of the wire, mercury, and battery was completed) (the wire; rotating; L:around the magnet)
the circuit of the wire, mercury, and battery the wire the wire
was completed began rotating
T:When the circuit of the wire, mercury, and battery was completed
L:around the magnet