Semi-cylindrical anamorphosis, A wild boar defends her young, Henry Kettle, 1775
Inv V09340, P02553

These kinds of paintings - called anamorphoses - clearly belong to physics as entertainment. The incomprehensible tangle of extended lines and surfaces is suddenly transformed into a pretty picture when a semi-circular mirror is placed on it. In the eighteenth century these optical jokes were all the rage. They came in all shapes and sizes: with conical and pyramid-shaped mirrors, with portraits, hunting scenes, but naturally also erotic scenes. The representation on this painting is quite civilised: a wild boar defends its young against dogs. Not surprisingly the panel comes from the scientific collection of the University of Leiden.