Fig. 1.2. Ronalds' Electrograph, possibly the first Electrostatic Recording Apparatus ever built. (Taken from Encyclopaedia Britannica, Vol. 8, 1842. Permission granted to reproduce.)
1.3.5 breath figures. In 1838 Riess6 noticed that glass or mica plates placed between spark discharge points and sparked show branched patterns when breathed upon. The patterns stand out mirror-bright upon the surface fogged by the breath. Four years later, in 1842, Karsten discovered a method of producing breath images of coins or metal engravings. A coin was placed on a glass plate which rested on a grounded metal disc. Electric sparks from a static machine were applied to the coin for about 100 revolutions of the machine. When the coin was removed and the glass was breathed upon, the glass surface showed a complete image of the design, with the areas which had been in close contact with the raised areas of the metal showing dark or transparent while the
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