 The concept of an electrostatic generator in which charge is mechanically transported in small amounts into the interior of a high-voltage electrode originated with the Kelvin water dropper, invented during 1867 by William Thomson (Lord Kelvin), in which charged drops of water fall into a bucket with the same polarity charge, adding to the charge.In a machine of this type, the gravitational force moves the drops against the opposing electrostatic field of the bucket.Kelvin himself first suggested using a belt to carry the charge instead of water.