Small Tesla coil a resonant transformer circuit invented in 1891 by Nikola Tesla which produces high voltage, high frequency electricity. Owned by William Thompson, Lord Kelvin, who did some of the first mathematical analysis of resonance in electrical circuits. Shown producing streamers between two loops of wire attached to the output terminals. Caption: ""Tesla oscillation transformer (Tesla coil) presented by Lord Kelvin before the British Association August 1897. This small and compact instrument, only 8 inches high, developed 2 square feet of streamers from 25 watts from the 110 volt DC supply circuit. The instrument contains a Tesla primary and secondary, condenser, and a circuit controller.