For the continuous production of electrostatic charges and high D.C. potentials in the laboratory. Two plastic disks of 300mm dia have a series of metal foil segments attached radially to them. These disks are contra-rotated by a simple hand operated belt drive. Induced charge built up on the foil segments as the disc rotates is picked up by the metallised cloth wipers rubbing against them and transferred to the discharge arms. Two Leyden jar capacitors can be linked via a simple moving contact to the discharge arms. These enable higher potentials to be obtained between the discharge arms. It produces sparks upto 50mm under appropriate conditions.