The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com         13. July 2008 2 Reproductions of Kinraide's Electrical Spark Gap US Patent 623,318 Filed Sept 24, 1898 - Originally shown in US Patent 623,316 Filed May 5, 1898 UK Patent No. 5518, A.D. 1899, Filed 14th Mar 1899;  Also Patented in Germany Water-Cooled Quenched Spark Gap 2 Complete Spark Gaps Click here for a video! Lever moves bottom plate higher or lower Delta posts allow positioning of plates in the exact same plane Disassembled The copper jugs are filled with water to keep the electrode cool. The sparks form between 2 6" plates.  These are aluminum, the originals were copper. A piece of graphite placed on the gap shows the patterns of spark erosion produced... Top view.  Cork is removable to fill with water! Bottom view - I used bakelite. Thomas Burton Kinraide - Originator of the later "Quenched Gap" used in wireless telegraphy (Telefunken gap, later modified by Wein) Kinraide minding a stopwatch for an X-Ray... The delicate adjustment of this gap produces unusual discharges. The original tank circuit used only 900V!