The history of the development of the subject is first outlined, and methods of operation of cables are described. The technical side is introduced with a statement of the various conditions whi h limit operation of cables, and a general method of analysis is developed, based upon an extension of ordinary alternating-current theory. The theory is made use of to analyze the action of cable types and of apparatus which at this time can be regarded as standard. The fundamental theory of the method of analysis, with information on the calculation of transients in electrical circuits, is given in the Appendix.