DRAKE'S ELECTRICAL DICTIONARY LOWE Drake's Electrical Dictionary A Compendium of Words, Terms and Phrases Used in the Electrical Trades and Electrical Engineering By PAUL E. LOWE, M. E. Assisted by a Corps of Electrical Engineers and Writers on Electrical Subjects CHICAGO FREDERICK J. DRAKE & CO. Publishers UG Copyright 1915 By Frederick J. Drake & Co., Chicago " -*- .' PREFACE The prime object of DRAKE'S ELECTRICAL DICTION- ARY is to bring together for convenient reference the words, terms and phrases used in the electrical world. The tremendous growth in interest in the electrical arts, trades and sciences makes some method of quick reference a practical necessity. It is hoped that the manner of presentation "followed in this book will prove to be most advantageous. Many practical difficulties arise in arranging all words and phrases alphabetically. The single words fall into place naturally enough, but in placing the phrases the question of which word of the phrase is to have the alphabetic position is important. The gen- eral plan of using the first words of all phrases has been adopted. Thus an endless number of annoying cross references have been avoided. In any field of science in which growth has been and continues to be so rapid, it is only natural that words and terms are not absolutely fixed. Without making the work too voluminous, however, we have endeavored to include all those words and terms in common use, though many are used interchangeably. Every effort has been made to produce a book of the greatest practical utility to every one who has any in- terest in the subject of electricity. 3O2QPO ELECTRICAL DICTIONARY. A A. C. An abbreviation expressing an alternating current. Absolute. Complete by itself. Independent of any other element. Absolute Unit of Current. A current possessing a de- gree of strength, and which when transmitted through a wire which has been curved in the shape of an arc of a circle of one centimetre radius, will act on a one-unit power magnetic pole, stationed at the center of the arc, with a force equal to one degree. A 10 amperes current. Absolute Unit of Electromotive Force. The electro- motive force unit C. G. S. Absolute Vacuum. A void produced by the exhaustion of all residual gases. Absorption. The act of one form of material substance sucking or drawing in some other form of matter. The sucking in of water by a sponge or the draw: ing in of vapors, gases, light, electricity, energy or heat by any other material substance. Absorption Power. A property peculiar to certain ma- terials by which they draw in gases through their pores and condense them. Acceleration. The increase or decrease of motion or action. The time period of mutation in velocity. 1 2 ; \ ELECTRICAL DICTIONARY Accumulated Siectricity.-r-Electricity confined or stored as in a condenser. Accumulating Electricity. Confining or placing elec- tricity in storage. Accumulation of Electricity. The gathering of elec- tric charges in condensers or Leyden jars. An electric charge augmented by aid of a device term an accumulator. A charge produced by the use of an influence machine. The gathering of electricity by storage batteries or accumulators. Accumulator. A term sometimes used to designate a current accumulator. A condenser, a Leyden jar, a storage battery. Acetometer or Acidometer. A graduated hydrometer used to ascertain the strength of acetic acid or vinegar. Achromatic Lens. A lens producing images without false coloring. Acidometer. (See Acetometer.) Acoustic. Pertaining to the sense of hearing,or sound. Acoustic Absorption. The absorbing by one vibrating object or mass of the sound-wave energy created by another vibrating object or mass. Acoustic Interference. Mutual influence of sound- waves upon each other. Acoustic Synchronizer. A contrivance employed to mark the synchronism of two alternating currents. An acoustic apparatus in which at synchronism silence is effected. Actinic. Pertaining to chemical changes produced by ELECTRICAL DICTIONARY 3 the sun's rays, or radiators from other sources of energy. Actinic Photometer. A photometer which determines the intensity of light by the quantity of decompo- sition which is chemically obtained in it. Actinic Ray. Any form of radiating energy having the property to induce chemical action. Actinometer. An apparatus for determining the de- gree of energy in the chemical effects of light. Active Coil or Conductor. A coil or conductor con- veying a current of electricity. Active Current. The active constituent of a current in an alternating current circuit, in contradistinc- tion from the wattless component of current. Active Electromotive Force. That constituent of the impressed electromotive force in an alternating current which is employed to surmount the ohmic resistance, in contradistinction from the compon- ent employed to overcome the induced C. E. M. F. Active Material Storage Cell. The matter which de- composes while charging or discharging in a storage or secondary cell and which performs the function of storing electricity. Active Plate of Voltaic Cell. A term applied to the zinc and other metallic plates used in voltaic or primary cells, and which dissolve in the process of active operation. Active Polar Surface of Magnet. The surface of a mag- net which emits or absorbs the useful flux. Active Wire. The section of wire on the armature of a dynamo which goes through the inducing mag- 4 ELECTRICAL DICTIONARY netic flux, in contradistinction from the "idle wire," or the remaining wire which does not pass through the flux. Activity. Power. Rate of performance. Performance per second in invariable operation. Actual Efficiency. Efficiency answering commercial purposes. Acute Angle. An angle less than 90 degrees, or less than a right angle. Adapter. A threaded projection attached to an incan- descent electric lamp by means of which the lamp can be screwed to gas fixtures in the place of gas burner. A device enabling a lamp of any one manu- facture to be fitted into the socket of the lamp of every other manufacture. An apparatus contrived to modify the continuous electric current used in incandescent service, in order that the mild contin- uous currents employed in electro-therapeutics may be obtained. Adhesion. An attraction existing between heteroge- neous molecules in contradistinction from cohesion or the mutual attraction of homogeneous mole- cules. Adhesion, Electric. The adhesion of two surfaces re- sulting from the attraction of dissimilar electro- static charges. Adhesion, Magnetic. The adhesion of surfaces result- ing from magnetic flux. Adhesive Tape. A tape rendered adhesive by the ap- plication of an adhesive insulating material, and used to protect bare conductors at joints and other exposed points. ELECTRICAL DICTIONARY 5 Adiabatic Expansion. The expansion of a gas in a chamber whose walls receive no heat from the gas nor convey any to it differing tlius from isothermal expansion. Adjustable Condenser. A condenser, the capacity of which is susceptible of variation within prescribed limits. Adjustable Resistance. A resistance, the degree of which is easily varied within prescribed limits. Adjustable Rheostat. A resistance readily adjusted. Adjustable Vacuum Tube. A vacuum tube designed for X-ray examinations; the vacuum in which is diminishable by heat acting upon a vaporizable substance. Adjuster for Lamp Pendant. A device of any descrip- tion suitable for making adjustments or changes in altitude or position of pendant lamps. Adjusting Cleat. A cleat susceptible to adjustment with reference to altitude or alignment. Adjustment. Any change in an apparatus which will insure correct performance of its office. Adjustment of Relay. That regulation of a receiving relay which insures ready response to signals for- warded over the line. Aerial Circuit. The section of a circuit composed of aerial lines or conductors. An elevated circuit of wire. Aerial Conductor. A conductor erected overhead. Aerial Line. A line erected overhead. Aerodynamics. The science which treats of the motion of air and its mechanical effect when in motion. 6 ELECTRICAL DICTIONARY Aero- Ferric Inductance. The inductance inherent in a coil, the magnetic circuit of which is composed in parts of air and iron. After Glow. A fluorescent glow visible in an exhausted container of glass after removal from electrostatic influence. Age-Coating of Electric Incandescent Lamp Chamber. A black coating from carbon and other like sub- stances deposited in the chamber of an incandescent lamp while in active service. Aging of Alcohol, Electric. The artificial aging of alcohol by subjecting it to the action of ozone gen- erated by electricity. Aging of Electric Incandescent Lamp. A diminishing by degrees of the capacity of an electric incandes- cent lamp resulting from either age-coating or im- pairment of the filament. Aging of Transformer. A diminution in the capacity of a transformer due to its core becoming old. Transformer fatigue. Agone. A line on the earth's surface on which the magnetic needle points to the true north, the mag- netic meridian coinciding with the geographical. Air Blast for Commutator. A blast of air played upon the surface of the commutator of an electric dyna- mo to obviate damaging flashes. Air Blast Transformer. A transformer which is kept cool by the application of an air jet. Air Churning. The motion of the air contiguous to the armature of a dynamo or motor while rotating, oc- casioning a loss of energy. Air Core Solenoid. A solenoid whose sole core is air. ELECTRICAL DICTIONARY 7 Air Gap. Any gap or aperture in a magnetic circuit which contains air only. Air Gap Commutator. The air space between the parts of contaction in an air-insulated commutator. , Air Insulation. Insulation procured by the action of air. Air Pump. A contrivance employed to withdraw the air and other gases from a vessel. Air Resistance of Dynamo. The mechanical resistance opposed by the surrounding air to the rotary mo- tion of a dynamo. Air Space. The space. existing between the polar sur- face within wiiic'h an armature rotates, and the surface of the armature itself. The space in a comb lightning arrester between the opposing sur- faces. Alarm Electric. Any electric contrivance which, work- ing automatically, directs attention, by the open- ing and closing of a circuit, to certain occurrences, i. e. : the movement of doors or windows, the reach- ing of certain prescribed limits in the rise and fall of temperature, footsteps in certain places, etc. A device used to summon a person to a telephone or a telegraphic instrument. "Alive." A term applied to live circuits or wires. Active circuits or wires. All-Night Arc Lamp. An arc lamp with a double carbon. Allotropic State. The property of substances of exist- ing in two or more conditions which are distinct in their physical relation, but without change in 8 ELECTRICAL DICTIONARY their chemical composition, i. e. : the various modi- fications of carbon. Alloy. Any compound of two or more metals, as of copper and zinc to form brass. Alternate Currents. Currents which alternate. Alternating. Having a periodical change in direction. Alternating Arc. An arc with alternating current. An arc which receives its supply from an alternating current circuit. Alternating Continuous-Current Commutating Machine. A secondary generator, which by aid of a commu- tator, is employed to change an alternating to a continuous current. Alternating-Current Dynamo-Electric Machine. A dy- namo-electric machine which produces in its ex- ternal circuit currents that alternate. Alternating-Current Electric Mo-tor. A motor impelled by currents that alternate. Alternating-Current Electro-Magnet. An electro-mag- net, the coils of which are traversed by alternating currents, and whilst continually reversing in mag- netism, yet maintains a constant attraction for the armature. Alternating-Current Phase-Meter. -An apparatus em- ployed to determine the phase difference between two alternating currents. Alternating-Current Power. Electric power furnished with alternating currents. The result of the effi- cient alternating current force, the energy of pres- sure under which the current is obtained, and the power factor. ELECTRICAL DICTIONARY 9 Alternating-Current Pressure Indicator. An alternat- ing current volt-meter. Alternating-Current Regulator. A contrivance em- ployed to regulate the pressure of an alternating current generator, with a view to maintaining con- stancy. A regulator employed to govern the strength of an alternating current. Alternating-Current Transmission. Transmission of power by the use of alternating currents. Alternating Currents. Currents flowing in opposite di- rections and alternating. Currents which reverse their direction periodically. Alternation. A change of direction. A change of di- rection by an electro-motive current. One vibration instead of an entire cycle or a double vibration. Amalgam. A compound of mercury or quick silver with any other metal. Amalgam, Electric. A substance used to cover the rub- bers of frictional electric machines. Amalgamate. To convert into an amalgam. Amalgamation of Zinc. A salt of mercury solution used in amalgamating the zincs of voltaic batteries. Amber. A yellowish, resinous substance found as a fossil in alluvial soils. American Morse Code. The telegraphic code invented by Morse, and used almost exclusively in the United States. American Wire Gauge. The name by which the Brown & Sharpe wire gauge is known, in which the diam- eter of the largest wire, No. 0000, is 0.46 inches, and wire No. 36, 0.005 inches, and all other diam- eters progress geometrically. 10 ELECTRICAL DICTIONARY Ammeter. Any sort of galvanometer which can meas- ure the strength of currents in amperes directly. Amorphous. Devoid of definite crystalline form. Amperage. The num'ber of amperes which pass through a circuit in a stated time. Ampere. The accepted unit of electric current. A flow of electricity at a rate which transmits one coulomb per second. The current which could pass through a circuit that offered a resistance of one ohm under a one-volt electro-motive force. Ampere-Hour. A unit of quantity equal to the amount of electricity transmitted by one ampere flowing during one hour. Ampere-Hour Efficiency of Storage Battery. The rate between the ampere-hours consumed from and those supplied to a storage battery in a cycle of charge and discharge. Ampere-Turn. A unit of magneto-motive force equal to the force resulting from the effect of one am- pere passing around a single turn of wire. Ampere's Rule for Deflection of Needle. The deflection of the north-seeking pole of a magnetic needle by a current at the left of an object assumed to be facing the needle from a point in the current. Amyloid. A material used itf making incandescent lamp filaments and which is obtained by subjecting cellulose to the action of sulphuric acid. A cellu- lose parchment. Amyloid Filament. A filament made of amyloid. Analysis. The resolution of any object into its con- stituent or original elements in order to determine its composition. ELECTRICAL DICTIONARY 11 Analysis Electric. The resolution of a compound sub- stance into elementary constituents by electrical process in order to determine its composition. Anchored Filament. A means providing for the sup- port of an incandescent lamp filament at its center in order to obviate injury by too violent vibration. Anemometer. An instrument for measuring the force and velocity of the wind. Anemometer, Electric. An instrument for recording "the force and direction of the wind by use of elec- tricity. Aneroid Barometer. An instrument for measuring at- mospheric pressure, the action of which, depends upon the varying pressure of the atmosphere upon the elastic top of a metallic box from which the air has been exhausted. Angle. The difference in direction of two lines in the same plane that meet in a point or that would meet if sufficiently extended. Angle of Lead. The forward angular departure from the established position, which the collecting brushes must be required to undergo on commu- tator of a continuous current generator, to the end, that quiet commutation may be obtained. Animal Magnetism. A term applied to the phenomena of hypnotism, mesmerism, etc. Annealing. A process for softening metals by first heating and then permitting them to cool gradu- ally. Annealing, Electric. An annealing process by means of electric heat instead of heat produced in the or- dinary way. 12 ELECTRICAL DICTIONARY Annunciator Board. A board equipped with annunci- ator drops. Annunciator Drop. A signal, which when it drops, an- nounces the closing or opening of the circuit of an electro-magnet connected with the annunciator. Annunciator Wire. Insulated wire of a kind adaptable to annunciator circuits. Anode. The positive pole of an electric battery, or preferably the path by which the current passes out and enters the electrolyte on its way to the other pole; opposed to the cathode. Anomalous. Deviation from a general rule. Abnor- mal. Irregular. Anomalous Helix. A helix wound in such manner as to create an anomalous magnet. Anomalous Magnet. A magnet having more than two free poles. Anomalous Magnetization. The magnetization which the vibrating discharge of a Ley den jar or conden- ser produces. Magnetization from which more than two free poles in a magnet result. Answering Jacks. The jacks in a panel of a telephone switchboard which are connected with those sub- scribers whose calling drops are in the same panel, in order that each call may be promptly answered at a contiguous jack. Anti-Induction Telephone Cable. A telephone cable which, by reason of a particular arrangement of its conductors, neutralizes the effects of induction caused by neighboring circuits. A telephone cable which is protected from the effects of electrostatic ELECTRICAL DICTIONARY 13 induction from adjacent circuits by a covering of metal which is grounded at fitting intervals. Antimonious Lead. A compound of lead and antimony, which, being proof against the action of a charging current, is used for the grid of a storage battery. Aperiodic. Not possessing periodicity. Attaining re- pose without vibrations. Aperiodic Galvanometer. A galvanometer the needle of which attains repose without vibrations. A dead-beat galvanometer. Apparent Electro-motive Force. The apparent acting of the E. M. F. in a circuit, as measured by the drop of pressure occasioned by the resistance of the circuit, and the force of current flowing through it. Aqueous Solution. Substances dissolved in water. Arc. A segment of a circle. A voltaic arc. Arc. To discharge in voltaic arc form. Arc-Circuit Cut-Out. A cut-out used in a series arc- light circuit to obviate the breaking of the whole circuit in the event of the extinguishment of any one lamp. Arc-Lamp, Electric. An electric lamp which derives its light from the voltaic arc. An incandescent lamp used in observatories to light the circles of telescopes and other instruments. Arc-Lamp Hanger. A board from which an arc-lamp hangs and is equipped with electric connections. Arc-Lamp Spark-Arrester. A gauze protector enclos- ing the arc, to guard against fire where arc lamps are used in dangerous proximity to combustible ma- terfals, as in store windows. 14 ELECTRICAL DICTIONARY Arc-Light. The carbon voltaic arc light. Arc-Light Generator. A dynamo electric machine which supplies arc-light circuits with the current. Arc-Light Projector. An arc lamp provided with a re- flector for obtaining a beam of approximately par- allel rays of light. Arc Plug-Switchboard. A -switchboard equipped with spring-jacks contacts and which connect -with the terminals of various circuits and plug switches con- nected to dynamo terminals, so that the connection between any dynamo and any circuit can be made. Several circuits connected to the one dynamo, or several dynamos located in the same circuit. Arc Standard of Light. A standard obtained by means of the photometer, determining the inten- sity of the light which is given out by a certain predetermined crater area of the positive carbon of a carbon arc. Aerometer. An instrument for measuring the speci- fic gravity of fluids. Areometry. The act of measuring the specific gravity of fluids. Armature. A body of iron or other material suscep- tible to magnetization and which is placed on or contiguous to the poles of a magnet. That part of a dynamo electric machine termed: the armature. Armature Bars. Heavy conductors used for armature windings. Heavy copper bars used instead of the usual wire windings on large drum armatures, and in form of rectangular cross-section strips. Armature Binding Wires. Wire coiled on the outside of the armature wires to preclude the separation, ELECTRICAL DICTIONARY 15 by centrifugal force of the armature wires from the core. Armature Bore. The space allowed for the rotation of an armature between the pole pieces of a dynamo. Armature Core. The body of laminated iron which carries the coil conductors of dynamos and motors. Armature Loop. The single conducting loop on a dyna- mo armature. Armature of Dynamo. An iron core around which is wound coils of insulated wire. That part of a dyna- mo which generates useful currents or differences of potential. The part of a dynamo which rotates between the field magnets or pole pieces. That part of the dynamo which generates E. M. Fs. by the magnetic flux successively filling and emptying the coils. Armature Pinion. A wheel with teeth attached to the armature shaft of a surface car motor, whose func- tion is to engage the teeth of the reducing gear. Armature Pockets. Spaces allowed in the core of an armature to receive the armature coils. Armature Projections. The sections of an armature core which intervene between the slots and pockets. Armature Reaction. The reactive magnetic effect, re- sulting from the action of the current in the arma- ture of a dynamo, on the magnetic circuit of the machine. Armature Slots. The slots in an armature core in- tended to receive the armature coils. Armature Spider. A frame-work of metal attached with keys to the armature shaft and equipped with 16 ELECTRICAL DICTIONARY arms projecting radially and serving to hold the armature cores solidly. Armature Stampings. Stampings of sheet iron em- ployed for the core discs on laminated armature cores. Armature Varnish. A varnish with insulating prop- erties used on armature windings to increase their resistance against friction and moisture. Armored. Protected by armor, as of cables protected by sheathing. Artificial Illumination. Light obtained from artificial sources. Astatic. Having no magnetic power of direction. Astatic Galvanometer. A galvanometer equipped with an astatic needle. Asynchronous. Happening or acting without simul- taneity. Asynchronous Alternating-Current Motor. A motor, the speed of which is not simultaneous with that of its driving generator ; the two machines having an equal number of poles. Atmosphere. The entire mass of aeriform fluid sur- rounding the earth. The weight or pressure of gas or fluid on a unit of surface: 14.73 pounds per square inch at sea level. Atmospheric Electricity. Electricity free in the atmos- phere. Atom. An ultimate particle of matter the smallest particle of simple matter. Atomic. Pertaining to or consisting of atoms. Atomize. The separation with an atomizer of a fluid into a spray. To reduce to atoms. ELECTRICAL DICTIONARY 17 Attachment Plug. A plug introduced into a screw socket, or spring jack, to facilitate the connection of lamps, etc., to a circuit. Attract. To draw to. Attraction of Gravitation. The attraction of force by which all bodies or particles of matter in the uni- verse tend toward each other. The attraction of the earth which causes all bodies of lesser mass within its influence to fall upon it. Attractions and Repulsions of Currents. The attrac- tion or repulsion exerted by active circuits upon one another, due to the mutual action of their mag- netic fields. Aurora. A luminous meteoric phenomenon appearing only in the night, displaying itself in streams and flashes of light, ascending toward the zenith from a dusky bank a few degrees above the northern hori- zon. Aurora Australis. A light similar to the Aurora Bore- alis, appearing in the southern skies. Aurora Borealis. The northern light. Automatic Make-and-Break. A contrivance which en- ables the to-and-fro movement of the armature of an electric magnet to make and break its circuit automatically. Automatic Overload- Switch. An automatic electro- magnetic switch introduced in a circuit which causes it to open automatically when the discharg- ing current surpasses a fixed, safe limiting force. Automatic Regulation of Dynamo Electric Machine. That regulation of a dynamo electric machine which automatically maintains, invariable, the 18 ELECTRICAL DICTIONARY strength of current, or the potential difference at the terminals. Automatic Regulation of Motor. That regulation of a motor which preserves its speed constant. Automatic Circuit-Breaker. A contrivance by means of which a circuit it automatically opened when carrying an excessive current. Automatic Cut-Out for Storage Battery. An automatic electro-magnetic switch, introduced into a storage battery's charging circuit, in order that the charg- ing circuit may be opened in case the current fails to enter the batteries. Automatic Fire-Alarm. A device so adjusted as to telegraph automatically an alarm of fire from any place when its temperature is increased above a certain degree. Automatic Telephone Exchange. A telephonic ex- change operated upon a system which enables the subscribers to communicate with each other in- dependent of an operator. Automatic Telephone Hook. A telephone switch which operates automatically when the receiver is taken off or hung upon it. Automatic Time Cut-Out. A contrivance for automat- ically cutting a translating device or a source of electric power from a circuit after the expiration of a certain predetermined time. Automobile. Containing the power of self movement. Automobile Torpedo. A torpedo containing the power to propel itself. Auxiliary Bus. An auxiliary pressure to which a cen- ELECTRICAL DICTIONARY 19 tral station bus-bar is connected. Not the main station pressure ; but one differing from it. Average Efficiency of Motor. The efficiency of an elec- tric motor founded on its mean load. The ratio of a motor's performance in a specified time to the electric power it has consumed in the same time. Average Life of Incandescent Lamp. The average length of time that a number of incandescent lamps, on a circuit of specified pressure, will burn without breakage. B. S. G. An abbreviation of British standard gauge. B. & S. W. G. An abbreviation of Brown and Sharp 's wire gauge. B. T. U. An abbreviation of British thermal unit. B. W. G. An abbreviation of Birmingham wire gauge. Back Pitch. The pitch backward of the windings of an armature. Back-Turns of Armature. Turns of an armature cur- rent which have a tendency to demagnetize the field. Back ampere turns. Backward Pitch of Armature Windings. A pitch in- variably left-handed when viewed from commuta- tor side. Bad Earth. A name given to a bad ground, or an earth connection with a comparatively strong electric re- sistance. Baking Oven, Electric. A bake oven heated by elec- tricity. 20 ELECTRICAL DICTIONARY Balance Photometer. A photometer founded on the dissolution of iodide of nitrogen by the process of light action. Balanced Armature. An armature having its weight apportioned with regularity as referred to its axis of rotation. An armature set in order by the use of additional weights, so that its weight is appor- tioned uniformly as referred to its axis of rotation. Balanced Load. A load uniformly apportioned to two or more generating units as observed in the poly- phase systems of distribution, or the three-wire, five-wire, multiple. Balanced Polyphase System. A polyphase system with all its branches proportional with reference to their electro-motive force and phase. Balanced Resistance. A resistance arranged in a bridge in such a manner that it will be balanced by the residuary resistance in the bridge. Balancing Coil of Armature. A subsidiary field-wind- ing in series with an armature with its magneto-mo- tive force equal and opposite to that of the arma- ture current, obtaining zero as the total magnetic effect upon the field, leaving the field flux un- changed no matter what the load. Balancing Resistance for Dynamos. A governing re- sistance possessing a range adequate to the balan- cing of one dynamo against another with which it is worked in parallel. Bank of Lamps. An assemblage of electric lamps to- gether in a common structure, ordinarily with a view to acquiring a load. Bank of Transformers. An assemblage of transformers together in a common structure, ordinarily with a ELECTRICAL DICTIONARY 21 view, either to acquire a load, or to modify the pressure. Bar Armature. An armature the conductors of which are constructed of bars-. Bar Electro-Magnet. An electro-magnet with its core presenting the appearance of a straight bar or rod. Bar Windings. Armature windings constructed of copper bars. Bar- Wound Armature. An armature the conductors of which have the shape of bars. Bare Carbons. Arc light carbons which are not electro- plated with copper. Barometer. An instrument for determining the weight or pressure of the atmosphere. Barometric Column. A column ordinarily of mercury, about 30 inches in perpendicular, supported in a barometer by the pressure of the atmosphere. Bar Winding of Armature. A winding composed of copper bars joined together at their extremities and insulated. Basis Metal of Electro-Plating. A metal upon the sur- face of which a deposit is to be made by electro- plating. Battery. A term often applied to an electric battery. Battery Gauge. A movable galvanometer appropriate for common battery-testing work. Battery Jar. A jar employed to hold the electrolyte of each separate cell of a primary or secondary bat- tery. Battery Lamp. An incandescent lamp which by reason 22 ELECTRICAL DICTIONARY of its low voltage can be worked by the voltage of a battery having a few series-connected cells. Battery Motor. An electric motor wound in such man- ner as to admit of operation by a comparatively low power, such as that of the common battery. Battery of Generators. Several generators connected in such manner as to obtain the action of a single generator. Battery Solution. The fluid or electrolyte of the pri- mary or secondary cell. Battery Syringe. A syringe employed for emptying a voltaic battery of acids or liquids which have lost their potency, or for replenishing it with live liquid. Becquerel Radiation. A radiation discovered by Bec- querel, which is invisible and which is given out by some salts, notably salts of uranium, and which has the power to permeate many opaque bodies im- penetrable by ordinary light, and affecting a photo- graphic plate. Bega. The prefix for one billion, one thousand million or 10 9 . Beg-Ohm. A billion ohms. One thousand megohms. Bell-