BOILLY Louis Leopold (draughtsman) after - Lot 196

BOILLY Louis Leopold (draughtsman) after Madame Danton and her son looking at optical views through a zograscope Color lithograph 53 x 44 cm (view) Note: The young woman is traditionally given for Louise-Sébastienne Gély, second wife of Georges Danton, and the child for Antoine, son of the tribune's first marriage. The painting was exhibited at the Salon of 1793. (Claire Dalzin, 2016) The child looks at optical views through a zograscope. This "recreation" of observing the view through an optic has its origins in technical progress. It wasn't until the early 18th century that it became possible to manufacture biconvex lenses with a diameter greater than the average eye spacing (ten to twelve centimetres). As well as producing optical instruments for scientific purposes, such as microscopes and telescopes, spectacle makers also produced "optics". It was undoubtedly George Adams, one of London's leading spectacle makers, who coined one of the terms used for optics in England: the zograscope (from the Greek zôo, "life", and -graphos, "which describes"). Light rays, refracted by the lens, enter the viewer's eyes in parallel, creating an impression of distance from the viewer. The latter must be placed at a distance equivalent to the focal length of the lens (Musée des Arts précieux Paul Dupuy).