The fourth and last edition of this book was published in 1967. Although it has been out of print for many years it is still considered the "Bible" of contact theory and is referred to in almost every scientific paper dealing with electric contacts. This classic book serves as a basis for understanding of contacts and their use in technology. It contains fundamental theory, critical information and a richness of details including a pertinent literature list. A chapter is devoted to the tunnel effect, several chapters treat such friction and wear phenomena which are closely connected with the theory of electric contacts. Subjects covered include tarnishing of contact material, fritting of tarnish films in contacts, material transfer in switches and commutation, and the theory of thermal contacts.