This volume is especially prepared for self-instruction in the art of designing direct- and alternating-current machinery. Care has been taken to remain strictly within the province of design; the reader being assumed to possess knowledge of the principles of electricity and magnetism, and to be familiar with the theory of operation of electrical machines. The designs are carried out according to methods developed in actual practice and are supplemented by data and dimensions of lines of machines actually built by several of the largest American and European companies. The book is divided into two parts: one treating the design of direct-current machines, and the other that of alternating-current machines; each part being followed by a list of questions which clearly bring out the important points to be remembered.