THE publishers state that this book is intended to fill a gap existing among the books available for students and industrial physicists. In general, the subject-matter concerns the elements of optical instruments. Of the six chapters, the first three, entied “Reflection and Refraction”, “Focal Length Measurements” and “The Telescope”, are mainly devoted to descriptions of experiments, illustrating simple instruments and measurements, to be carried out with spectacle lenses and small prisms. In all work of this kind an optical bench is needed, and the author recommends a steel metre rule set on its edge. In the chapters on “The Microscope” and “Photographic Lenses” less use is made of this method ; in the latter, a historical account of the early development of photographic objectives is offered, with suggestions of methods for detecting defects in them, and in the former, magnification, resolution, numerical aperture and illumination are among the subjects considered. The final chapter, on “Optical Glass: its Working and Testing”, contains a very short account of glass working, the measurement of refractive indices, curvature, and miscellaneous prism angles, and other workshop operations. The book contains several articles likely to be of interest to teachers of physics ; but for the industrial physicist it will be found much less useful than the “Dictionary of Applied Physics”, which points out the precautions needed to obtain accurate results. A few developments which have taken place since the “Dictionary” appeared are included in the present volume ; but the treatment of them is much too brief to be of practical value. The author does not appear to be familiar with present-day practice and knowledge in some of the subjects he has treated. The mathematics is often badly set out and is not always correct, and a, number of other errors have been noted.