made in England
These brass hemispheres, known as Magdeburg hemispheres, were used to demonstrate features of atmospheric pressure. They were made in England in the 19th century and are unsigned.
When used in demonstration, the hemispheres are placed together and the air pumped out. The external atmospheric pressure outside makes them very difficult to separate.
The hemispheres are named after Otto von Guericke (1602-86) of Magdeburg in Germany, who was the first to perform this demonstration described in 1657.
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