The whole subject of the chemical production of electricity is discussed in Electrolysis (Vol. 9, p. 217), by W. C. D. Whetham, of the technical staff of Cambridge University. Battery (Vol. 3, p. 531), fully illustrated, deals with all the forms of primary battery, and Accumulator (Vol. 1, p. 126), also illustrated, by Walter Hibbert, of the London Polytechnic, with all the secondary types. The alkaline accumulators, of which the Edison apparatus is a well known type, are the subject of a special section. Turning to mechanically produced electricity, the first article to read is Electromagnetism (Vol. 9, p. 226). This brings you naturally to the article Dynamo (Vol. 8, p. 764), by C. C. Hawkins, author of one of the best practical text-books on the subject. This copiously illustrated article, in length equivalent to 50 pages of this Guide, discusses continuous current dynamos, lap-winding, commutators, field-magnets, forgings and castings for magnets, air-gaps, armature cores, carbon brushes, cooling surfaces and alternators.
Having thus covered the subject of obtaining current, the group of articles next to be considered is that dealing with its measurement and the examination of resistances. The general article Units, Physical (Vol. 27, p. 740), contains a section on electrical units. Then come Potentiometer (Vol. 22, p. 205); Meter, Electric (Vol. 18, p. 291); Voltmeter (Vol. 28, p. 206), illustrated; Amperemeter (Vol. 1, p. 879), illustrated; Ohmmeter (Vol. 20, p. 34); Wattmeter (Vol. 28, p. 419); Galvanometer (Vol. 11, p. 428), illustrated; Electrometer (Vol. 9, p. 234), illustrated; Electroscope (Vol. 9, p. 239), illustrated; Wheatstone’s Bridge (Vol. 28, p. 584), illustrated; and Oscillograph (Vol. 20, p. 347), illustrated.
Lighting Appliances
The commercial supply of current is covered by a series of articles of which the first to be read is Electricity Supply (Vol. 9, p. 193), to which Emile Garcke, the famous electrical engineer, contributes a section. Power Transmission, Electrical (Vol. 22, p. 233), is by Louis Bell, chief engineer of the General Electric Co., Boston; and contains full details as to the use of both two-phase and three-phase generators in transmission. Induction Coil (Vol. 14, p. 502) and Transformers (Vol. 27, p. 173) are both fully illustrated. Lighting, Electric (Vol. 16, p. 659) deals with arc, incandescent and vapour lamps, and with wiring. The section on household work gives excellent practical information about the best arrangements of lights. A special class of electric light supplies is discussed in Lighthouse (Vol. 16, p. 627), by W. T. Douglass, who erected the new Eddystone and the Bishop’s Rock lights, and by N. G. Gedye, another practical expert.
The appliances used to convert current back again into the mechanical energy from which it had been derived are described in the article Motors, Electric (Vol. 18, p. 910). This article divides continuous current motors into five classes: Separately excited; series-wound constant current; series-wound constant potential; series-wound interdependent current and potential; and shunt-wound constant potential. Alternating current motors are similarly classified as Synchronous constant potential; induction-polyphase constant potential; induction monophase constant potential; repulsion commutating, and series-commutating.
Trolley Cars and Railroads
Machinery for applying electric power to transportation, both for trolley cars and heavy railroad traffic, is described in the article Traction (Vol. 27, p. 118), by Prof. Louis Duncan, who designed the first electric locomotives employed with large loads—those introduced in 1895 by the Baltimore & Ohio R.R. for its track in the tunnel under Baltimore. The article gives, with many mechanical diagrams, accounts of the appliances by which the current is taken from trolley wires, conduits and third rails, and of the types of motors and controllers employed. Crane (Vol. 7, p. 368), by Walter Pitt, describes the peculiar type of “crane-rated” motor, by the aid of which steam and hydraulic cranes can be displaced. The electric furnaces used for the reduction of ores and for manufacturing processes in which exceptionally high temperatures are required, are treated in Electrometallurgy (Vol. 9, p. 232), by W. G. M’Millan, lecturer on metallurgy at Mason College, Birmingham. Electric machinery for the refining of metals is dealt with in the article Electrochemistry (Vol. 9, p. 208). Under Surgical Instruments (Vol. 26, p. 133) there is a description of the apparatus used for cautery and for illuminating parts of the interior of the body. The appliances used in Electrotherapeutics are dealt with under that heading (Vol. 9, p. 249). Information as to other medical and surgical apparatus will be found under Röntgen Rays (Vol. 23, p. 694), X-Ray Treatment (Vol. 28, p. 887), by Dr. H. L. Jones, of St. Bartholomew’s Hospital, London; and Fluorescence (Vol. 10, p. 575), by Prof. J. R. Cotter, of Trinity College, Dublin.
Telegraph and Telephone
Telegraph (Vol. 26, p. 510), equivalent in length to 70 pages of this Guide, and fully illustrated, is by a number of contributors, and discusses both land lines and submarine cables. The section on instruments, by H. R. Kempe, electrician to the General Post Office, London, includes a full description of the transmitters and receivers employed in the various systems of wireless telegraphy. Telephone (Vol. 26, p. 547) deals with the fixed and portable instruments, the batteries and switchboards, the new automatic exchange “selectors,” and with special applications of the microphone.
A number of other electric appliances are discussed in separate articles, such as Bell (Vol. 3, p. 692), by H. M. Ross, in which burglar alarm devices are described; and Ventilation, Fan (Vol. 27, p. 1011), by James Bartlett; while sparking plugs and other ignition appliances are treated under Oil Engine (Vol. 20, p. 35).