Seitz symbols for crystallographic symmetry operations.

The aim of this report is to describe the Seitz notation for symmetry operations adopted by the Commission on Crystallographic Nomenclature as the standard convention for Seitz symbolism of the International Union of Crystallography. The established notation follows the existing crystallographic conventions in the descriptions of symmetry operations.

Optical properties of X-rays--dynamical diffraction.

The first attempts at measuring the optical properties of X-rays such as refraction, reflection and diffraction are described. The main ideas forming the basis of Ewald's thesis in 1912 are then summarized. The first extension of Ewald's thesis to the X-ray case is the introduction of the reciprocal lattice.

60 years of IUCr journals.

In the 60 years since its birth in 1948, the number of journals published by the International Union of Crystallography has risen from one to eight. A brief account of the history of the forerunner of the IUCr journals, Zeitschrift für Kristallographie, is given. The context of the birth of the IUCr and the first of its journals, Acta Crystallographica, is recalled.

A note on Bragg-case Pendellösung and dispersion surface.

It is usual to state, since Ewald [Ann. Phys. (1917), 54, 519-597], that Bragg-case Pendellösung involves two wavefields belonging to the same branch of the dispersion surface.