SIGNOR PIZZETTI has treated the subject of geodesy in a thoroughly exhaustive manner. The theoretical portion of the book, dealing with the formulae used in geodesy, is very ably demonstrated, and the mathematical proofs of the various problems are sufficiently clear to be easily followed by those practically uninitiated in the subject. The same, however, cannot be said of the descriptive narrative of geodetical operations in general. The book, in fact, impresses one far more from the theoretical than from the practical point of view. The absence of practical demonstrations of the use of the various formulae must be a great loss in a work of this nature, and for this reason it compares unfavourably with such standard treatises as Puissant's “Traite de Geodesie” and Clarke's “Geodesy,” where ample practical illustrations of the application of geodetical formulae are given to help the student in this complicated subject. Even a few examples taken from any modern geodetic triangulation would have been of the greatest assistance. Theory alone is almost bound to have a deterrent effect. Trattato di Geodesia Teoretica. By Paolo Pizzetti. Pp. ix + 467. (Bologna: Zanichelli, 1905.)