(p. 130) . . . in the early 1870s Hermann Sprengel, a German chemist working in London, invented a device that came to be called the Sprengel mercury pump. This was the crucial invention that actually made household illumination possible. Unfortunately, only one person in history thought Hermann Sprengel deserved to be better known: Hermann Sprengel. Sprengel’s pump could reduce the amount of air in a glass chamber to one-millionth of its normal volume, which would enable a filament to glow for hundreds of hours. All that was necessary now was to find a suitable material for the filament.
Source:
Bryson, Bill. At Home: A Short History of Private Life. New York: Doubleday, 2010.
(Note: ellipsis added.)