The problem of determining the orientation of Widmanstetter figures has recently arisen in a paper by Dr. L. J. Spencer on the Gibeon shower of meteoritic irons in South-West Africa: the method of attacking it to be described here will be applied to the crystals illustrated in plate II of his paper.

By producing the faces of a regular octahedron in all possible directions a set of six congruent prisms is formed, as shown in fig. 1. The Widmanstetter figures are the traces of these prisms in a plane of section. The section across any one of the prisms by a plane normal to its axis is a rhomb whose angles are those of a face of the rhombic-dodecahedron, that is to say, 70° 31′ and 109° 28′.