3614200 Jean Jallabert investigating the effects of points and knobs on electrical discharges, from Les Merveilles de la Science, pub.1870 by French School, (19th century); (add.info.: Jean Jallabert, 1712-1768, investigating the effects of points and knobs on electrical discharges whilst standing on a wax insulating platform, one hand touching an electrostatic generator and the other holding a pointed piece of wood. When its point neared one end of a conducting rod mounted on a pivot, the deflection of the rod caused by the discharge showed whether there was a positive or negative charge. From Les Merveilles de la Science, published 1870.); French, out of copyright.