CROS (Charles). General solution of the problem of colour photography. Paris, Gauthier-Villars, 1869. Large in-8, paperback, printed cover, red half-chagrin folder lined with velvet paper and slipcase (Devauchelle). First edition of the author's first book, the pioneering text for the invention of colour photography ("A landmark in the history of colour photography"). As on most copies, the selling price of 1 franc printed on the cover is covered: here 2 francs, the edition having remained unsold at the printer Gauthier-Villars for decades. Slight spotting on the cover.