Two Boatmen in a Marsh near a Cluster of Trees, c. 1857. Unlike most clich?-verres, which are similar to line drawings, Dutilleux's thirteen works in this medium are extremely tonal. The artist described them as "monochrome paintings on glass for photography." Instead of scratching the design into the opaque ground covering the glass plate, as Corot or Daubigny had done, Dutilleux created the image by painting the plate with it.