Reviews and abstracts

Abstract

This second volume of Traité de Géodésie, devoted to geodetic astronomy, fills a definite void in the modern literature. In recent years we have had such works as those of Roelofs and of Nassan in English, and of Niethammer in German, but none of these was intended to give definitive coverage of a field in which the variations from classical practice are too often concealed in dry statistical reports and tabulations.Tardi and Laclavère have striven to provide concise developments of the theory fundamental to geodetic astronomy without skimping and yet without becoming overspecialized. Thus the section on astronomic refraction deals intensively with the theory for refraction over the range of zenith distance suitable for precise work but does not become mired In the more complex analysis required near the horizon where the conventional series expansion fails to converge. Perhaps the twenty pages or so on precession and nutation are too condensed, yet enough is given so that the significance of the quantity (C ‐ A)/C In one of the many overlapping problems of astronomy and geodesy is clear. Additional material on this are a will no doubt be included in the treatment of latitude variation promised for Tome III. Another commendable inclusion is the discussion of the recent results showing the variability of the Earth's rate of rotation, and the subsequent adoption of ‘Ephemeris Time’ for certain purposes.