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马格德堡半球（指一对铜质半球, 合拢后形成一中空圆球; 如抽去其中空气, 半球极难分开, 从而验证大气压力的存在）。
词源
early 19th cent.: named after the city of MAGDEBURG, home of the inventor, Otto von Guericke （1602-86）.