In 1676, French scientist Jean Picard noticed that when he moved his mercury barometer in the dark, a faint, diffuse, purplish light appeared around the meniscus—but only when the mercury in the tube moved downward, enlarging the vacuum space. Only some of the attempts to reproduce the effect were successful, and interest lapsed until 1700, when John Bernoulli at the University of Groningen demonstrated the importance of having the mercury purified and the meniscus clean. Bernoulli scaled up the effect by using a large glass vial evacuated with an air pump and sealed with a cork and wax; he called the vial his “perpetual phosphorus.” Six years later, in 1706, Francis Hauksbee in London went further, hooking up a glass globe, evacuated and partly filled with mercury, to a driving belt. Subsequent experiments showed similar effects with pieces of amber (“elektron” in Greek) inside the revolving globe and with...

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