Macedonio Melloni (1798, 1854) first used an optical bench for measurements of radiant heat. Starting from a principle of analogy between light and heat he used this instrument to investigate the propagation laws of the infrared radiation. The bench was built in Paris by Ruhmkorff and, after Melloni's death, was given by the widow to the School of Phisics of the University of Naples. It consists of a graduate brass bar, 1 meter long, fixed to a base of mahogany wood. The base, 61 cm long and 18 cm wide, is provided with four levelling screws. The equipment includes 46 components such as thermoelectric piles, shields and light and heat sources (Locatelli's lamp, Leslie's cube, etc.). Most components may be set on the bench or on a side-arm movable in a horizontal plane. By alternating these components, Melloni was able to perform a series of experiments which allowed to define many properties of the radiant heat and to agree to the identity between light and heat. The components may be kept in a wooden parallelepipedic box provided with double bottom and entirely lined with red velvet. The sizes of the box are 104x26x17 cm. Well-preserved. Signed: "Ruhmkorff, rue des Orfevres, Paris". c. 1840.
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