Diagrams, geometrical diagrams by [Arthur] Cayley Four hand-drawn diagrams in pencil and ink, the largest showing a circle on an axis labelled 30-180. A series of lines radiate from the diameter of the circle, one of them labelled 'meridian'. The other diagrams show a circle, a triangle and a graph relating to plane geometry. Each diagram is reproduced as an engraved print. Subject: Mathematics / Plane geometry The printed diagrams were published in volume 37 of the Proceedings of the Royal Society alongside the paper 'On the non-Euclidian plane geometry'. 1884