Engraving depicting Davy's experiment with a mercury

Engraving depicting Davy's experiment with a mercury vapour light. A long u-tube contains two columns of mercury: both ends of the tube are immersed in cups of mercury. When an electric current is passed through, the air between the columns glows with a feeble bluish light. Heating intensified the light, and the introduction of air bubbles changed it to purple. Davy concluded that the light was due to glowing mercury vapour

Bluish Bubbles Changed Concluded Contains Cups Current Davy Davys Ends Feeble Glow Glowing Glows Heating Immersed Intensified Introduction Mercury Passed Vapour

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