This volume is intended for those who have such a knowledge of direct currents as is given by Volume I. It presupposes no knowledge of alternating currents. The first two chapters are devoted to the development of the fundamental laws of alter nating currents and alternating-current circuits. Subsequent chapters consider the application of these fundamental laws to alternating-current measurements, to polyphase circuits, to alternating-current machinery, and to power transmission. A chapter on illumination and photometry has been included, as a brief discussion of the underlying principles of light and of light measurements is important in a general course in electrical engineering.