SNOBOL 3 primer. An introduction to the computer programming language by A. Forte

transition-metal compounds and covalent non-transitionmetal compounds. Again, the important chemical aspects (length of the C-N-group, structure relations and disorder in ionic solids, shape and dimensions of cyanic complexes, donor-acceptor bonds) are clearly brought out and the general rules emerging from the data are presented. The topic of this paper cuts through established lines of text books on crystal chemistry and thus provides the reader with new links of thought. Both articles discussed above should be valuable for lectures on structural chemistry. The third contribution on Structures of Natural Products (68 pages, 250 references, more than 165 molecular drawings) by A. McL. Mathieson is arranged quite differently: It is directed towards the organic chemist and much less towards the interested outsider. An enormous wealth of structural results (about 200 determinations) is presented according to generic groups (porphyrins, alkaloids, terpenes, mould products). The very condensed treatment thoroughly illustrated by many formulae is almost exclusively in terms of molecular conformation, the metrical aspects of molecular structure being omitted. This authoritative compilation will certainly be of great help to the expert, but the non-specialist gets the impression of a beautiful piece of music, whose themes pass by too rapidly. The introductory chapter gives a precise and well-stated discussion of the possibilities and limits of X-ray diffraction. This first volume has shot far towards the goal and sets 'perspectives' in the wide field of structural chemistry. Chemists and crystallographers should be grateful to the editors and authors for undertaking this task. TI-mO HAHN lnstitut fiir Kristallographie Technische Hochschule Aachen 51 Aachen Templergraben 55 Germany