This book is a comprehensive guide to understanding electricity, magnetism, and electro-magnetism. Jean-Baptiste Biot, a prominent French physicist in the 19th century, compiled this treatise as part of a natural philosophy course for students. The second part of the course, it covers all the latest discoveries and improvements in the field. Whether you're a student of physics or simply interested in learning more about the world around you, this book is an essential read. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.