Originally published in 1954, as part of the Cambridge Monographs on Physics series, this book presents a detailed study of the properties of ferromagnetic substances. After an introductory survey the text considers in detail the various factors affecting the behaviour of individual domains. It is then shown how, by paying attention to certain effects of demagnetizing fields, a consistent picture can be built up of the way in which the domains are combined in actual ferromagnetic substances. In later chapters it is revealed that the observed behaviour of ferromagnetic materials depends on the laws governing individual domains, with particular reference to experiments, including those of the author which show this depends in a simple form. This book will be of value to anyone with an interest in ferromagnetism, industrial physics and the history of science.