Photographs in natural colours are next described, and their history is traced from 1810 when Seebeck of Jena made experiments described in Goethe’s famous work on Colours. The first successful colour photography was by Becquerel in 1848 on a daguerreotype plate, chlorinized. The later methods of Lippmann and Lumière, respectively, with collodion dry plates prepared with albumen and with dyed gelatin plates (orthochromatic), produce pictures in which the colours show only from an angle.
The section on the Action of Light on Chemical Compounds, with a plate showing spectra and graduation scales, contains valuable diagrams and a chronological table of observers of the action of light on different substances. The paragraphs of particular interest to the practical photographer are those on:
Measurement of the Rapidity of a Plate.
Effect of Temperature on Sensitiveness.
Effect of Small Intensities of Light on a Sensitive Salt.
Effect of Very Intense Light on a Sensitive Salt.
Intermittent Exposure of a Sensitive Salt.
Effect of Monochromatic Light of Varying Wave-Lengths on a Sensitive Salt.
Reproduction of Coloured Objects by 3 Photographic Positives: Ives’ process; Joly’s process; Autochrome of Lumière; Positives in 3 Colours.
Another division (equivalent to 60 pages at least in this Guide) of the article is on Apparatus. It deals especially with the hand camera as developed from 1855 to 1888 when the Eastman Kodak came out. And it has separate paragraphs on Focusing; Plate-holders or Dark-slides (1 illustration); Studio cameras; Portable and Field cameras; Hand cameras (7 illustrations); Twin-lens and Reflex cameras (2 illustrations); Panoramic cameras (2 illustrations); 3 Colour cameras (1 illustration); Enlarging cameras and cinematographs.