Experiment with Magdeburg hemispheres, 1654.

Engraving taken from 'Experimenta Nova' (1672) by the German scientist Otto von Guericke (1602-1686), showing his experiment with an evacuated sphere being carried out at Madgeburg, Germany. In this demonstration 16 horses could not pull apart the two halves of an evacuated sphere, which became known as Magdeburg hemispheres. On 8 May 1654, he performed the experiment before the Reichstag. A scaled down version became a standard demonstration carried out with vacuum pumps.