The frictional electrification of droplets was discovered by accident in 1840, when the driver of a steam locomotive (itself a new technology) working in a colliery near Newcastle in northeast England, put his hand near a jet of high-pressure steam escaping from the boiler, and discovered that when he touched the boiler with the other hand, he received an electrical shock and saw a spark. A Newcastle lawyer, William Armstrong (1810-1900, and later an engineer and ordnance manufacturer) investigated the phenomenon systematically by placing the boiler on glass legs and directing the jet of steam toward an insulated metallic conductor. The conductor became positively charged, while the boiler acquired a negative charge.
The cut at the left, above, shows the hydro-electrical generator developed by Armstrong soon after the discovery. The boiler was about 150 cm long and 60 cm in diameter. A later machine at the Polytechnic Institution in London could produce a spark about 55 cm in length.
The example at the right, above, is in the Deutches Museum in Munich. I have seen similar machines at Teyler's Museum in Haarlem in the Netherlands, and in storage at the National Museum of History and Technology of the Smithsonian Institution.
A hydro-electrical machine is shown in the frontispiece of Noad's 1844 book on electricity.
REF: Thomas B. Greenslade, Jr., "Nineteenth Century Textbook Illustrations LV, The Hydro-Electrical Machine", The Physics Teacher, 32, 210-211 (1994)
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