Needle, compass

“Bring the two ends of the wire into contact, and thus close the circuit. The needle instantly flies around as though it was trying to place itself at right angles to the wire. Break the circuit, and the needle swings back to its north and south position. Twist the wires together, and bend the conductor into a loop so that the current passes above the needle in one direction and beneath the needle in the other direction. The deflection of the needle will be greater than before.” — Avery, 1895

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