Magdeburg vacuum experiment. Illustration of the experiment carried out in the 1650s in Magdeburg by German engineer and physicist Otto von Guericke (1602-1686). This demonstration of atmospheric pressure placed two brass hemispheres together with the air pumped out from between them, forming a vacuum. The external atmospheric pressure forcing the hemispheres together was so strong that not even sixteen horses could pull them apart. Artwork from 'Chaudieres et Machines a Vapeur' (1911) by French civil engineer Max de Nansouty (1854-1913), part of the 'Les merveilles de la science' series of 1867-1891 by Louis Figuier.