Traité pratique de photographie au charbon : complété par la description de divers procédés d'impressions inaltérables, photochromie et tirages photomécaniques
A French technical manual by photographer Léon Vidal, published in Paris in 1877, teaching carbon printing and related photomechanical processes to photographers and printers. Its engravings show laboratory instruments and test apparatus, drawn in plain black line with hatched tonal fields, so a designer could borrow their precise diagrammatic clarity for scientific or instructional layouts.
