On certain Improvements on Photographic Processes described in a former Communication, and on the Parathermic Rays of the Solar Spectrum. Received November 17, - Read November 17, 1842.

(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.