Prague: J.G. Calve, 1835-36. First edition of the memoir in which Cauchy gave a quantitative explanation of dispersion on the basis of the wave theory of light – dispersion refers to the different angles through which a ray of light is refracted by a transparent medium, depending on its wavelength. Cauchy gave in this work the relation, now named after him, between the refractive index of a transparent medium and the wavelength of light.
The memoire in which Cauchy explained the dispersion of light from the undulatory theory of light, and first derived the equation, named after him, relating the refractive index and wavelength of light for a particular transparent material. This memoire was a continuation of his earlier work, of the same title published in Paris in 1830, and was issued as eight parts of his periodical ‘Nouveaux Exercices de Mathématiques’ (see below).
“The dispersion of light when passing through matter without getting fully absorbed, i.e., the variation of the refractive index n (which denotes the ratio of the velocity of light in vacuo to the velocity of light in matter) with the wavelength, always played an important role in the history of optics since the times of Isaac Newton. After the undulatory theory of light won over the corpuscular view in the beginning of the nineteenth century, Augustin Louis Cauchy proposed an explanation of the dispersion phenomenon, based on the assumption that matter consisted of molecules having finite distances from each other (Cauchy 1836). According to his theory the refractive index n increased with decreasing wavelength λ of the light - n was approximately proportional to λ-2 - in general agreement with the data on what was later called ‘normal’ dispersion.” (Mehra & Rechenberg: The Historical Development of Quantum Theory, Vol. 1, Part 2, p. 630).
“The first livraisons appeared successively during the year 1835, at Prague. The first is a repetition of the ‘Memoire sur la dispersion’ [Paris, 1830]. In the second, (besides other discussions) is contained the actual deduction of the formula for dispersion. In September, 1835, [Cauchy] circulated a lithographed memoire on interpolation, (a translation of which appears in the Journal of Science, Vol. VIII. p. 459) in which he gives a calculation by that method, of Fraunhofer’s indices for one kind of flint glass, but without any theoretical explanation. In the ‘Nouveaux Exercices’ for 1836, he gives in detail his most elaborate and exact method of computation, and applies it with perfect success to all the indices determined by Fraunhofer” (Baden Powell: A General and Elementary View of the Undulatory Theory, as Applied to the Dispersion of Light, London, Parker, 1851, pp. XLVI-XLVII).
“In 1826 Cauchy began to publish his ‘Exercises de Mathematiques’, which was essentially a mathematical periodical consisting entirely of papers written by himself; it appeared at approximately monthly intervals until 1830. He used similar series as vehicles for his publications at later stages of his career; the ‘Nouveaux Exercices de Mathématiques’ were published in Prague in 1835-36 and the ‘Exercices d'Analyse et de Physique Mathématique’ appeared at intervals from 1840 to 1853.” (Smithies: Cauchy and the Creation of Complex Function Theory, p.113).
4to: 259 x 202 mm. Contemporary half calf over marbled boards, marbled end papers, engraved bookplate to front paste down, hinges worn but still strong, head and tale of spine professionally repaired, in all a very nice copy. (IV: title and forword to the Exercices), IV(: title and forword of the memoire), 236 pp. Scarce.