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Edison and Francis Jehl reenacting the evacuation of an experimental light
bulb during dedication ceremonies at Dearborn.
In the picture, Jehl is pouring mercury into a network of glass tubes; this was an effective evacuation pump (designed by Edison on the basis of pumps by Heinrich Geissler and Hermann Sprengel) that sucked air out of the light bulb.
SI negative #87-1732
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