There is a remarkable cubic graph of 28 vertices, discovered by Prof. H.S.M. Coxeter, which has no circuit of fewer than 7 edges and in which all oriented arcs made up of three edges are equivalent under the automorphism group.

The structure of the graph is as follows. There are three disjoint heptagons A(a1a2a3a4a5a6a7a1), B(b1b5b2b6b3b7b4b1) and C(c1c6c4c2c7c5c3c1). We denote the seven remaining vertices by d1, d2,…, d7. For each suffix i the three edges incident with dijoin it to ai, bi and ci. In drawing a diagram of the graph it seems best to show only the heptagons A, B and C, leaving the rest of the figure to the imagination.

The purpose of this note is to establish another property of the graph, that it has no Hamiltonian circuit.