English: The Kelvin water dropper, an electrostatic generator invented by William Thomson, Lord Kelvin, in 1867, that works by dripping water. This drawing, appearing in many early textbooks before 1900, may be the original form of the apparatus. It consists of a water supply pipe (c, d, e) that drips two streams of water drops. Each stream falls through a cylindrical metal charging electrode (A, B) and then into a metal funnel (a, b), from which it drips to the floor. Each metal funnel is connected to the other stream's charging electrode, and to a Leyden jar capacitor (cylindrical objects sitting on ground), to store the charge.