"HERSCHEL, JOHN W.F. - THE DISCOVERY OF THE IRON-PRINTING PROCESS.
Reference : 42662
(1843)
(London, Richard and John E., Taylor, 1843. 4to. No wrappers as extracted from ""Philosophical Transactions"" 1843 - Part I. Pp. 1-6.
First appearance of a pioneer-paper in the history of early photography, as Herschel here for the first time describes his discovery of the iron printing process with ammonio-citrate of iron by both methods, namely with blue lines on a white background and white lines on a blue ground.