Magdeburg hemispheres
Concise Oxford English Dictionary © 2008 Oxford University Press:
Magdeburg hemispheres
▶plural noun a pair of copper or brass hemispheres joined to form a hollow globe from which the air can be extracted to demonstrate the pressure of the atmosphere, which then prevents them from being pulled apart.
– origin C19: named after the German city of Magdeburg, where they were invented.
'Magdeburg hemispheres' also found in these Oxford entries:
