Book excerpt: Prism and Lens Making: A Textbook for Optical Glassworkers, Second Edition is a unique compendium of the art and science of the optical working of glass for the production of mirrors, lenses, and prisms. Incorporating minor corrections and a foreword by Professor Walter Welford FRS, this reissue of the 1957 edition provides a wealth of technical information and hands-on guidance gained from a lifetime of experience. Although some of the techniques have been replaced by more modern methods, this classic book is still a valuable source of practical assistance as well as being a pleasure to read. About the Author Frank Twyman was a skilled craftsman in all aspects of optics. He joined Otto Hilger in 1898 to work on the production of simple spectroscopes costing less than £10 each. After the death of Otto Hilger, Twyman became Managing Director of Adam Hilger Ltd., a company known for the finest quality optical and mechanical work. He worked here from 1902 to 1946 and was very concerned with the practical aspects of instrument making; he designed many of the instruments himself and constantly strove to improve the techniques of optical grinding and polishing. In 1916 Twyman and Alfred Green, the foreman of the Hilger optical shops, patented the now-famous prism and lens testing interferometer that bears their names. Twyman also undertook fundamental studies in the annealing process for glass and invented new spectrophotometers and spectrographs.