The application of electron theory to the structure and properties of metals and alloys has aroused much interest in recent years, but presents great difficulty to the non-mathematical reader. This book is intended for those to whom the ordinary textbook treatment is unattractive. It is divided into four parts dealing with the structure of atoms, metals, alloys and atomic nuclei, and is presented in the form of a dialogue between an Older Metallurgist and a Young Scientist, bringing out clearly the contrast between the old and the new viewpoints. Many difficulties are discussed and the dialogue is framed to give the reader continual help in understanding the problems at issue.Although written primarily for the metallurgical reader, the book should prove valuable to many others as an elementary introduction to modern atomic theory, while for students it may serve as an easy introduction to the more formal treatment of the standard textbooks.This revised impression has been corrected where necessary, and a number of revisions have been made where new work since 1948 has rendered the original description incorrect.