"Portrait sud de Notre-Dame de la Barre-Oeuvre. Negatif par Le secq. Photoghraphié sur [process] Lemercier, Lerebourgs, ….. [Impriemiere] (vers 1852) epreuver avant le ……Lemercier
"Of the few inventors who achieved halftone images, the first were the chemists Barreswil and Davanne, who worked in cooperation with the optician Lerebours and the lithographer Joseph Lemercier. In 1852 they took up the asphalt process by Joseph Nicéphore Niépce again, replacing the metal plate with granular lithographic stone, which they coated with asphalt ether solution rather than lavender oil. After exposure under the negative, ether was used as a solvent. The stone was then etched and colored. The areas where the asphalt, which was insoluble by the action of light, had prevented the action of the acid, took on the color. In 1854 Lemercier published the first six prints under the title "Lithophotographie", each 33 x 23 cm in size, … The prints showed good halftone values, but the process was later abandoned in favor of Poitevin’s, as only small editions could be printed "(H. Gernsheim). – For LCA Barreswil (1817-1870) cf. also Poggendorff I, 105.