N the present book I have tried to meet the needs of those readers who require an advanced text covering both the theoretical and practical sides of: the subject, as far as this can conveniently be done in a single volume. Though complete in itself, the book is not intended for beginners, who may be supposed to have read one of the excellent elementary treatises available, such as Whetham's Theory of Experimental Electricity. Space saved from the detailed treatment of elementary topics has been used to give an account of some of the more recent developments of electricity. It thus comes about that the book falls naturally into two sections; the first eight chapters having been kept fairly simple and containing all the principles necessary for a right appreciation of the subject, while the remaining chapters form introductory accounts of special subjects, which may be consulted by students before starting on treatises devoted to them alone.