FOR MERCHANTS AND MANUFACTURERS OF ELECTRICAL MACHINERY AND SUPPLIES
[Sidenote: Construction and Operation]
Electrical machinery and supplies include three main groups of
appliances: The apparatus by which electricity is originally generated;
the apparatus by which current is transmitted and, if necessary,
modified before it is used; and the infinitely various appliances for
its final employment. In connection with any one of the latter,
information may be needed as to its structure and its mechanical or
electrochemical method of operation, or as to its uses, and in the
treatment of these two aspects of a vast number of subjects the
advantages of the encyclopaedic plan of the Britannica are obvious. One
article will explain the method by which the same principles are applied
to a number of different machines. Another article will deal with a
group of appliances all used for similar purposes; and a reference to
the Index of 500,000 entries (Vol. 29) will at once guide the reader who
turns to the name of any electrical appliance to either kind of
information he desires at the moment, whether he wants to know how the
machine is made and operated, or what kind of work it does and how
efficiently it does it.
The reader to whom this chapter is addressed is already familiar with
the general subject of electricity, but he may at any moment desire to
review or to supplement his general knowledge in connection with some
new appliance which, for the first time, applies to commercial use one
of the many and intricate laws of electrical vibration. The whole
subject of the nature and action of electricity is outlined in the
article ELECTRICITY (Vol. 9, p. 179), by Prof. J. A. Fleming, of the
University of London, one of the world’s foremost authorities. In a
space equivalent to hardly more than 30 pages of this Guide, the field
covered in detail by many other articles is so concisely and clearly
surveyed that you get a complete view of the theoretical and practical
developments by which electrical science and industry have reached their
present position. The same contributor then considers ELECTROSTATICS
(Vol. 9, p. 240) and ELECTROKINETICS (Vol. 9, p. 210); and, in
CONDUCTION, ELECTRIC (Vol. 6, p. 855), deals with metallic,
non-metallic, dielectric and gaseous conductors. One section of this
article is by Sir J. J. Thomson, winner, in 1906, of the Nobel Prize for
Physics. The form in which metal is chiefly employed for the conduction
of electricity is the subject of a separate article, WIRE (Vol. 28, p.
738); and the articles on the individual metals deal with their
electrical properties.
[Sidenote: Batteries and Dynamos]
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.
[Sidenote: 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_.
[Sidenote: 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.
[Sidenote: 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).
There are also a number of appliances used mostly in experimental and
educational work. Such, for instance, are ELECTRICAL OR ELECTROSTATIC
MACHINE (Vol. 9, p. 176), with many illustrations; ELECTROPHORUS (Vol.
9, p. 237), and LEYDEN JAR (Vol. 16, p. 528).
The metals, chemicals and other materials sold by dealers in electrical
supplies, and their properties and uses, are described in COPPER (Vol.
7, p. 102), ZINC (Vol. 28, p. 981), LEAD (Vol. 16, p. 314), SULPHURIC
ACID (Vol. 26, p. 65), SODIUM, _Compounds_ (Vol. 25, p. 341); CHROMIUM
(Vol. 6, p. 296); NITROGEN, _Compounds_ (Vol. 19, p. 715); SAL AMMONIAC
(Vol. 24, p. 59), BICHROMATES AND CHROMATES (Vol. 3, p. 912), CARBON
(Vol. 5, p. 305), RUBBER (Vol. 23, p. 795), and GUTTA PERCHA (Vol. 12,
p. 743).
The following is a partial list, in alphabetical order, of articles of
peculiar interest to dealers in electrical supplies.
Accumulator
Amperemeter, or Ammeter
Armature
Battery
Bell
Bichromates and Chromates
Carbon
Chromium
Condenser
Conductor, Electric
Copper
Dielectric
Dynamo
Electricity
Electrical, or Electrostatic, Machine
Electricity Supply
Electrokinetics
Electrolysis
Electromagnetism
Electrometer
Electrophorus
Electroscope
Electrotherapeutics
Fluorescence
Fuze, or Fuse
Galvanometer
Gutta Percha
Induction Coil
Lead
Leyden Jar
Lighting
Meter, Electric
Motors, Electric
Nitrogen, _Compounds_
Ohmmeter
Oil Engine
Oscillograph
Potentiometer
Power Transmission
Röntgen Rays, _Apparatus_
Rubber
Sal Ammoniac
Sodium, _Compounds_
Sulphuric Acid
Surgical Instruments
Telegraph
Telephone
Thermometry, _Electrical_
Traction, _Electric_
Tramway
Transformers
Units, Physical
Vacuum Tube
Ventilation
Voltmeter
Wattmeter
Wheatstone’s Bridge
Wire
Zinc