Publisher Information: 1842.
Herschel, John F. W. (1792-1871). Autograph letter signed to an unidentified correspondent [Samuel Hunter Christie (1784-1865)]. Collingwood [House, Hawkhurst], December 21, 1842. 3pp. 122 x 98 mm. Very good.
Excellent letter discussing photographic researches from Sir John Herschel, whose intensive investigations in photography and photochemistry during the late 1830s and early 1840s led to enormous advances in the field in its earliest days. Herschel coined the terms "positive" and "negative," invented new photographic processes and improved existing ones, and experimented with color reproduction.
Herschel's letter begins with a discussion of his latest photographic work:
"Having had 2 days fine sun I have prepared specimens of photographs illustrative of the last paragraphs of my paper about the mercurial preparations and of a process not yet described that results of which if they will keep appear to me of great beauty. May I request you to direct them to be placed on the library table or otherwise submitted for inspection of such members as they may interest on Thursday and then added to the collection of my other specimens in Mr. Robertson's hands with a request that he will keep them together."
Herschel refers here to one of the two important papers on photography that he submitted to the Royal Society in 1842: "On the action of the rays of the solar spectrum on vegetable colours, and on some new photographic processes" (Philosophical Transactions 132 : 181-214) and "On certain improvements on photographic processes described in a former communication, and on the parathermic rays of the solar spectrum" (Philosophical Transactions 133 : 1-6). These papers discussed Herschel's photochemical experiments with a wide range of organic and metallic materials, and announced his invention of two new photographic processes: the gold-based chrysotype and the cyanotype, an iron-based method using potassium ferricyanide. This last process, which produces white images on a blue ground directly onto paper, is the ancestor of the modern blueprint. Herschel described the working details of these processes fully in his second paper, to which he is likely referring in the present letter. The "process not yet described" probably refers to Herschel's experimental and ultimately unsuccessful mercury-based photographic process, which he christened "celanotype." Herschel's correspondent was mathematician and physicist Samuel Hunter Christie, who made important contributions to the study of magnetism; he served as secretary of the Royal Society from 1837 to 1843. See Schaaf, Out of the Shadows (1992), chs. 3-5 for a detailed discussion of Herschel's photographic researches, including excerpts from his unpublished scientific notebooks. Hannavy, Encyclopedia of Nineteenth-Century Photography (2008), p. 655.Book Id: 40222