Abel Niépce de Saint-Victor

Claude Félix Abel Niépce de Saint-Victor (26 July 1805, Saint-Cyr, Saône-et-Loire – 7 April 1870, Paris) was a French photographic inventor. Claude was an army lieutenant and the cousin of Nicéphore Niépce. He first experimented in 1847 with negatives made with albumen on glass, a method subsequently used by Frederick Langenheim for his and his brother’s lantern slides. At his laboratory near Paris, Saint-Victor worked on the fixation of natural photographic colour as well as the perfection of his cousin's heliographing process for photomechanical printing. His method of photomechanical printing, called heliogravure, was published in 1856 in Traité pratique de gravure héliographique. In the 1850s, he also published frequently in La Lumière.

Near-discovery of radioactivity
In the 1850s, Saint-Victor was developing color photography using light-sensitive metal salts, including uranium salts. In 1857, long before Henri Becquerel's discovery of radioactivity, Saint-Victor observed that, even in complete darkness, certain salts could expose photographic emulsions. He found that uranium salts were responsible for this anomalous phenomenon. Photographers in France, England, and Germany confirmed Niepce's findings regarding uranium. See, for example:
 * Mr. Peligot showed, to the French Society of Photography, prints made from uranium nitrate by Mr. Victor Plumier in: Bulletin de la Société française de photographie, 4 : 92 (1858). [in French] In the same volume, Mr. Delahaye also showed, to the French Society of Photography, prints made from uranium nitrate by himself and several others in:  Bulletin de la Société française de photographie, 4 : 205 (1858). [in French]
 * Fournier d'Albe, Edmund Edward, The Life of Sir William Crookes, O.M., F.R.S. (Cambridge, England: Cambridge University Press, 1923), p. 389.  From p. 389:  "Niepce de St. Victor had discovered that uranium salts possessed the property of storing up light and giving it out in the dark, and in 1858 I took what was perhaps the first radium photograph in this country, by writing with solution of uranium nitrate on a card, insolating it [i.e., exposing it to sunlight], and then putting it face to face in the dark with a sheet of photographic paper; the image of the writing was reproduced on the paper."
 * Hagen, O. (1858) (Anwendung des salpetersauren Uranoxydes in der Photographie [Use of the nitrate of uranium oxide in photography] ), Monatsberichte der Königlich-Preussischen Akademie der Wissenschaften zu Berlin (Monthly Reports of the Royal Prussian Academy of Science at Berlin), pp. 290–293. [in German] Reprinted in English as: Hagen, O. (1858 November 22) "On the employment of nitrate of uranium in photography," Journal of the Photographic Society of London, 5 :  75–76.
 * Further early photographers who confirmed Niepce's results are listed in footnote (11) on p. 56 of (Fournier & Fournier, 1999). Niépce recognized that the light that was exposing his photographic plates was neither conventional phosphorescence nor fluorescence, and that the salts could expose photographic plates long after the salts had last been exposed to sunlight. Niépce's superior, Michel Eugène Chevreul, recognized the phenomenon as a fundamental discovery, pointing out that uranium salts retained their power to expose photographic plates even after six months in the dark. In 1861, Niépce stated that uranium salts emitted some sort of radiation that was invisible to the human eye: Original : " … cette activité persistante … ne peut mème pas être de la phosphorescence, car elle ne durerait pas si longtemps, d'après les expériences de M. Edmond Becquerel; il est donc plus probable que c'est un rayonnement invisible à nos yeux, comme le croit M. Léon Foucault, … ."

Translation : " … this persistent activity … cannot be due to phosphorescence, for it [i.e., phosphorescence] would not last so long, according to the experiments of Mr. Edmond Becquerel; it is thus more likely that it is a radiation that is invisible to our eyes, as Mr. Léon Foucault believes, … ." Niépce mentions Edmond Becquerel, the father of Henri Becquerel, who would later be credited with the discovery of radioactivity. In 1868, Edmond Becquerel published a book, La lumière: ses causes et ses effets (Light: its causes and its effects), in which he mentioned Niépce's findings; specifically, that objects that were coated with uranium nitrate could expose photographic plates in the dark. On the controversy about whether Henri Becquerel knew about Niépce de Saint-Victor's earlier discovery of radioactivity in uranium, see:
 * Michel Genet (1995) "The discovery of uranic rays: A short step for Henri Becquerel but a giant step for science," Radiochimica Acta 70 / 71 : 3–12.  This was part of a special issue of Radiochimica Acta which was reprinted in book form as:  J. P. Adloff, ed., One Hundred Years After the Discovery of Radioactivity  (Munich, Germany: R. Oldenbourg Verlag, 1996); see pages 3–12.  Available (in part) on-line at:  Google Books.
 * J. Fournier and P. Fournier (1990) "A. Niépce de Saint-Victor (1805-1870), M. E. Chevreul (1786-1889) et la découverte de la radioactivité," New Journal of Chemistry, 14 (11) : 785–790.
 * Fournier, Paul and Fournier, Josette (1999) "Hasard ou mémoire dans la découverte de la radioactivié?" [Chance or memory in the discovery of radioactivity?], Revue d'Histoire des Sciences, 52 (1) : 51–80.  [in French] Available at:  Persée (France)
 * At about the same time that Henri Becquerel made his discovery, the English physicist Silvanus P. Thompson (1851-1916) independently observed that uranium salts emit a radiation that can penetrate opaque materials. See page 104 of:  Thompson, Silvanus P. (1896) "On hyperphosphorescence," Philosophical Magazine, 42 :  103–107.  (Thompson also mentions Niépce de Saint-Victor's findings.)
 * At about the same time that Henri Becquerel made his discovery, the English physicist Silvanus P. Thompson (1851-1916) independently observed that uranium salts emit a radiation that can penetrate opaque materials. See page 104 of:  Thompson, Silvanus P. (1896) "On hyperphosphorescence," Philosophical Magazine, 42 :  103–107.  (Thompson also mentions Niépce de Saint-Victor's findings.)