Otto von Guericke (1602-1686), German physicist, operating the first static electricity generator. His generator consisted of a large ball of sulphur (yellow). When the ball was rotated and a pad rubbed against it, sparks were observed. This device was constructed in 1663. In the background (upper right) is a vacuum sphere. In an experiment unrelated to his work on electrostatics, von Guericke designed two brass hemispheres and evacuated the air from them. The hemispheres, which were held together only by external air pressure, then held a large amount of weights (seen below the hemispheres). Illustration from Physique Populaire (1891), by E. Desbeaux.