Diagrams, geometrical diagrams and experimental equipment by Leonard Darwin Two diagrams of experimental apparatus, labelled figures 1-2, followed by 21 geometrical diagrams relating to Darwin's investigation into the method of examination of photographic lenses at the Kew Observatory. Includes notes to the engraver. Subject: Optics / Scientific apparatus and instruments Prints of these diagrams were published in volume 52 of the Proceedings of the Royal Society alongside the paper 'On the method of examination of photographic lenses at the Kew Observatory'. 1892