On the Chemical Action of the Rays of the Solar Spectrum on Preparations of Silver and other Substances, both metallic and non-metallic, and on some Photographic Processes. Received and Read Febrauray 20, 1840. (+) Note I- (III).- On the Distribution . - [INTRODUCING 'POSITIVE' AND 'NEGATIVE' IN PHOTOGRAPHY]

"HERSCHEL, JOHN W.F.

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(London, Richard and John E., Taylor, 1840. 4to. No wrappers as extracted from "Philosophical Transactions" 1840 - Part I. Pp. XII [including title-page of Philosophical Transactions" 1840 - Part I), 59 pp. (Note I- III pp. 51-59) and 2 plates. (one showing Herschel's telescope, lithographed" the other showing the heat spectrum of the sun in stipple engraving). First appearance of an important pioneer-paper in the history of early photography, in which subject John Herschel was one of the main contributors. The paper deals with the dynamical interplay between photochemistry and photography and is of the greatest importence in applied photography. The later sections of the paper deals with the spectrum of the sun, Herschel's so-called thermographical representation of the spectrum of the sun (with description of the Actinograph, invented by him), rendering the heat radiation visible in the spectrum. This first importent spectrum is reproduced here on one of the plates (in stipple engraving). In this paper he introduces the photographical concepts 'positive' and 'negative' to express, respectively, pictures in which the lights and shades are the same as in nature, or as in the original model, and in which they are opposite.For this large paper John Herschel was awarded the Copley archives winners Prize for 1840."The object which the author has in view in this memoir is to place on record a number of insulated facts and observations respecting the relations bothof white light, and of the differently refrangible rays, to various chemical agents whic have offered themselves to his notice in the course of his photographical experiments, suggested by the announcement of M. Daguerre's discovery.The terms "direct" and "reverse" are also used to express pictures in which objects appear, as regards right and left, the same as in the original, and the contrary.The principal objects of inquiry in the present paper.are the following. First, the means of fixing photographs, the comparative merits of different chemical agents.The means of taking photographic copies and transfers.The preparation of photographic paper.The chemical analysis of the solar spectrum forms the subjects of the next section in the paper."(Abstract).

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• Titolo: On the Chemical Action of the Rays of the Solar Spectrum on Preparations of Silver and other Substances, both metallic and non-metallic, and on some Photographic Processes. Received and Read Febrauray 20, 1840. (+) Note I- (III).- On the Distribution . - [INTRODUCING 'POSITIVE' AND 'NEGATIVE' IN PHOTOGRAPHY]
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