The Magdeburg hemispheres, a pair of large copper hemispheres, with mating rims which were sealed with grease and the air pumped out, the spheres contained a vacuum and could not be pulled apart by teams of horses. Designed by German scientist and mayor of Magdeburg, Otto von Guericke, to demonstrate the air pump that he had invented, and the concept of atmospheric pressure. Otto von Guericke originally spelled Gericke, 1602 - 1686. German scientist, inventor, and politician. From Les Merveilles de la Science, published 1870.