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Mercury Glow Demonstrator
USA, circa 1910
This glass tube, the size of a short, fat, pencil, demonstrates the phenomenon that started the modern study of electricity. It holds a blob of mercury, and a variable inner glass tube. Most of the air has been pumped out. When shaken, it glows. Early in 1676, Jean Picard (the well-known French astronomer) was moving a mercury barometer in the dark. He noticed a glow in the vacuum above the oscillating column of mercury. Francis Hauksbee studied this glow in a series of experiments starting in 1703 and culminating in the first modern electrostatic generator some years later. Throughout the 18th century, nearly all electrostatic machines used friction pads covered with electrical amalgam (a compound containing mercury) rubbed by or against various glass objects. These later machines are directly related to that first observation: friction between glass and mercury giving rise to electrical effects. This demonstration apparatus was made circa 1910, and is very similar to some of the first electrical demonstrations ever made. When it is moved or shaken in the dark, the electrical glow inside is very easy to see. |
| The Bakken A Library and Museum of Electricity in Life 3537 Zenith Avenue South Minneapolis, MN 55416-4623, USA Join our E-Mail List Contact Us Tele: 612-926-3878 Fax: 612-927-7265 |
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