First edition. This book is an in-depth study of the principles of electromagnetism and its applications in various mechanical devices. The author provides a comprehensive overview of the theory and practical applications of electromagnets, including their design, construction, and operation. He also discusses the electromagnetic theory of light and the relationship between electricity and magnetism. The book is divided into several chapters, each of which covers a specific aspect of electromagnetism, such as magnetic circuits, magnetic fields, electromagnetic induction, and the behavior of magnetic materials. Silvanus Thompson also includes numerous illustrations and diagrams to help readers understand the concepts presented.