KIRCHHOFF, G. et R. BUNSEN. - FOUNDING SPECTRUM ANALYSIS - DISCOVERING CESIUM - FRENCH EDITION.

Analyse chimique fondée sur les Observations du Spectre. Premier Mémoire.

(Paris, Victor Masson et Fils, 1861). Without wrappers. In: "Annales de Chimie et de Physique", 3e Series - Tome 52, Cahier Aout 1861. Pp. 385-508. (Entire issue offered). Kirchhoff & Bunsen's paper: pp. 452-486 and 1 double-page folded chromolithographed plate, showing spectroscope and 8 spectra, among these the spectra of Cesium.

First apperance in French of this fundamental papers, constituting the invention of Spectrum Analysis, and announcing the discovery of a new elements, Cesium, by using the new method of spectroscopy, developed by them. This technique, made possible by their invention of the spectroscope, is called "One of the most dashing advances of the human mind into the secrets of the composition of matter on earth and in cosmos"(Kedrow in "Spectralanalyse", 1961). The spectral lines proved to be a guide not only to the great world of the outer cosmos, but to the infra-tiny world within the atom. Balmer made the first steps in this direction (the Balmer-lines). The next year Kirchhoff and Bunsen published another memoir in which they announced the finding of another new element, Rubidium

"The two investigators advanced, as scientifically established, the law that the bright lines in the spectrum may be taken as a sure sign of the presence of the respective metals. This conclusion was rendered doubtly sure by the discovery in the mineral water of Durkheim, through the spectrum, of two new metals. From the blue and the red lines, by which they were recognized, they were named "Cæsium" and "Rubidium". While spectrum analysis, as a terrestrial science, was due equally to Kirchhoff and Bunsen, its celestial applications belong to Kirchhoff alone."(Cajori in "A History of Physics in its Elementary Branches", pp. 160 ff).

In a letter to Henry Roscoe, with whom Bunsen carried out a long importent series of photochemical researches, Bunsen wrote: "At present Kirchhoff and I are engaged in a common work which doesn't let us sleep....Kirchhoff has made a wonderful, entirely unexpected discovery in finding the cause of the dark lines in the solar spectrum, and increasing them artificially in the sun's spectrum, and inproducing them in spectra which does not have lines, and in exactly the same position as the corresponding Frauenhofer lines. Thus a means has been found to determine the composition of the sun and fixed stars with the same accuracy as we determine sulfuric acid, chlorine, etc., with our chemical reagents. Substances on the earth can be determined by this

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