The present volume attempts a more adequate treatment of variable electromagnetic fields and the theory of wave propagation. Some attention is given to the stationary state, but for the purpose of introducing fundamental concepts under simple conditions, and always with a view to later application in the general case. The reader must possess a general knowledge of electricity and magnetism such as may be acquired from an elementary course based on the experimental laws of Coulomb, Ampere, and Faraday, followed by an intermediate course dealing with the more general properties of circuits, with thermionic and electronic devices, and with the elements of electromagnetic machinery, terminating in a formulation of Maxwell's equations. This book takes up at that point. The first chapter contains a general statement of the equations governing fields and potentials, a review of the theory of units, reference material on curvilinear coordinate systems and the elements of tensor analysis, concluding with a formulation of the field equations in a space-time continuum. The second chapter is also general in character, and much of it may be omitted on a first reading. Here one will find a discussion of fundamental field properties that may be deduced without reference to particular coordinate systems. A dimensional analysis of Maxwell's equations leads to basic definitions of the vectors E and B, and an investigation of the energy relations results in expressions for the mechanical force exerted on elements of charge, current, and neutral matter. In this way a direct connection is established between observable forces and the vectors employed to describe the structure of a field.