These sketches, undated, were formerly attributed in our Archives to Andrew Elvins. They are in fact lithographs of observational skecthes by Warren De la Rue from 1856 April 20, as can be found in Camille Flammarion, La Planète Mars et ses conditions d'habitabilité, synthèse générale de toutes les observations..., vol. I (Paris: Gauthier-Villars et fils, 1892), p. 128, fig. 76, and p. 129, fig. 77, among other places.
