Salt water dimmer

[1][2] A dimmer consisted of a glass jar filled with salt water with a metal electrode at each end.

[4] The switchboard built at Her Majesty's Theatre, London in 1897 had a dimmer scale of 0 to 10, whereas gas lighting only had 3 levels.

[1] The salt water need to be refilled regularly, the metal electrodes corroded, and the dimmers emitted a strong smell.

[4][6] The dimmers were hazardous both because of the flammable gases produced and the potential for electric shocks.

[7] An example of a saltwater dimmer can be seen backstage at Alexandra Palace Theatre in north London.