1814-1879

German inventor who developed the Geissler tube and the Geissler mercury pump. Geissler learned glassblowing and settled in Bonn, where he made scientific instruments. The Geissler tube is a sealed glass tube containing a near-vacuum; the rarefied gas within shows the passage of electricity through it. These tubes became the forerunner of the cathode ray tube, later used in televisions and computer monitors.