None
D -nAHFINO. 291 -*^ Apparent Increase in Re- ■utance of a Gktlvanometer doe to, 849 Correction for, 296 Definition of, 284 Daniell's Cell, Description of, 210 Cell, Chemical Action in, 214 Cell, Constancy of E. M. F. in, 216 CeU, B. M. P. of, 211 Cell, E. M. F. of Standard, 411 Cell, Gravity, 212 Cell, Flemiog's Standard, 412 Cell, How to Prevent Local Action in, 217 Cell, Polarisation in, 216 Cell, Resistance of, 211 Cell, Standard, 411 Dead-Beat, Shielded, Direct-Read- ing Ghilyanometers, Ad- vantages of, 78 Decrement, Determination of Log- arithmic, when Damping is Yer^ Slight, 297 Logarithmic, 296 Definition of Alternating Corrent, 196 of the Ampere, 11 of Brush Discharge, 369 of Capacity, 300 of Capacity of Condenser, 302 of Condenser, 801 of Conductivity, 155 of Contact Potential Difference, 851 of the Coulomb, 289 of Couple, 283 of Difference of Potentials, 80 of Damping, 284 of Dielectric, 311 of Direction of Current, 14 of Efficiency of Current Gene- rator, 451 of Efficiency of Electric Light, 452 of Elastic Curve, 84 of Electric Density, 117 of Electromotive Force, 202 of the Farad, 307 of Galvanometer, note, 21 of Gkdvanosoope, note, 21 of Glow Discharge, note, 369 of HermetioEdly SeaJing, note, 20 — - of Horizontal Component of Earth's Magnetic Force, note, 55 — ^ of Hypotenuse, note, 88 ^— of Induotdve Action, 87 »— of the Jouk«, 461 Definition of Lines of Force, 48 of Logarithmic Decrement, 296 of Mi^etio Axis of a Needle, 37 —-^ of Magnetic Saturation, 388 — • of Moment of Couple, note, 283 of Moment of Inertia, 78 — ^ of North-seeking End of Mag- net, 16 of the Ohm, 140 of Parallax, note, 28 of Periodic Time of YihratioiL, 291 — ^ of Plane of Magnetic Meridian, note, 45 —^ of Potential Difference, 80 of Power, 441 — - of Quantity of Electricity. 495 Density Electric, Definition of, 117 Electric, Great at Pointed End of a Conical Condactor, 118 Electric, Greater near Edges of Flat Sheet of Metal, IIB — Electric, Measuring, bj means of Proof Plane, 117 Electric, Nought on Inner Sur- face of Closed Conductor, 118 — — Electric, Potential, and Quan- tity, Examples showing Difference between, 121 Dependence ci Bate of Loss of Charge on Dielectric Only, 346 Deprez, E. M. F. DUfefeDtial OalTMioineter, Latbuer Clark'1,150 OalTanometer, Mode of Ad- jnstiag, 150 — — Gblranometer, Principle oi, 148 — — QalTanometer, Saperiority of Wbeststone't Bridge oTer, 171 •— OalTanometer, Uw of Shimts with, 183 Dilate Salphoric Acid, Effect of Elecbx>l7Bis of, 15 Dindnation of Beststance of In* ralaAora with Increase of Temperature, 271 Direct Comparison with Tangent GalTanometer, Calibrating OaJyanometer by, 58 Beading GalTanome^ra, 76 Beading, Shielded, Dead-Beat GaTyanometers, Advant- ages of, 78 Direction of Cnrrent, Definition of, U ^— of Current in Add, Copper, and Zinc Yoltameters, 15 ^— ■ of Current in Magnifying Spring Ammetersand Volt- meters, Indication of, 389 — — of Cnrrent round Magnet, Connection between, and Poles produced, 17 ^— of Flow ol Electric Current, What is Meant by, 2 ——of Magnetic Force produced by Current in Flat Coil, 43 Disadvantage of Magnifying Spring Ammeter and YcMtmeter, 391 Disadyantages of CardeVs Volt- meter. 385 — — of Cunyngname's Ammeter and Voltmeter, 427 — of Electro - Magnetic Control Meters, 385 — of Orayity Control Meters, 892 — • of Permanent Magnet Meters, 876 of Siemens' Eloctro-dynamome- tor, 381 — of Thomson's Large Current Galyanometer, 54 Discharge, Brush, 369 Glow, note, 309 -^ Multiplyixig Power of Shunt used in Measuring, 349 Dispersion Photometer, 454 Distance Spark can be sent between Balls of Influence Machine, 871 Distinction between Conduction and Induction, 97 between Galyanometer and Galyaaoeoope, noitf, 21 DistrfliulJou of Magnetism in Per* manent Magnet^ Measur> ing,24 CH Power in a Circuit, 445 Disturbance, Magnetic, Shielding Galyanometers from Ex- traneous, 73 Drawing Curyes on Squared Paper, 31 Curyes to Correct Besnlts of Experiments, 34 Dry Pile, 372 Duplex Telegraphy, Besistanoe Boxes used in, 186 Dynamometer, Measuring Currents with Siemens' ifiectro-, 379 Siemens' Electro-, 377. (See also Siemens' Electro-I^ynamo- meter.) E 1?ABTH, Potential of. Arbitrarily -^ taken as Nought, 84 Earth's Magnetic Force, Definition of the Horizontal Compo- nent of, note, 55 Ebonite Electrophorus for giving Negative Chaxges^ 359 '— Electarophorus for giving Posi- tive Charges, 357 Pillars, Corrugating Sides of, 272 '— Pillars, Common Fault in Con- structing, 272 Besistanoe oi, 271 — Specific Inductive Capacity of, 310 Edelmann's Electrometer, Sug- Improvements in. Sf^- — — Modification of Thomson's Quadrant Electrometer, 130 Effect of Electrolysis of Dilute Sul- phuric Acid, 15 Efficiency Increases with Power in Electric Lamps, 458 of Arc Light, Measuring, 455 — — of Current Generator, Defini- tion of, 451 ——of Electric Light, Measuring, 45i of Incandescent Lamps, 458 Elastic Curve, Definition of, 34 Electric and Heat Conductivities, Comparison of, 158 Apparatus, Static, shotdd be En- closed in MetaUio Case, lOB INDEX. 497 Electric A.rc, IXescription of, 188, 454 Arc, Meaaariug niaminating Power of, in any Plane, 457 Arc, Potential DUl'erence Re- quired to maintain, be- tween Two Carbons, note, 871 Charge, 109. (See Charge.) Circuit, Work done in, 199 — — Conductivity Diminishes more Kapidly thaa Heat Con- duotivi^, 159 —— Current. (See Current.) — — Density. (See Density.) Energy. (See Energy.) — Lamps, Description of Arc and Incandescent, 454 Lamps, Efficiency of, Increasing with Power, 458 Light, Measuring Efficiency of, 452 Potential. (See Potential.) Quantity. (See Quantity.) Bparks. (See Sparks.) Electrical Macoines, Frictional. {See Machines.) — — Machines, Influence. (See Ma- chines.) — Units, Ohm only one yet LegaliFed, 140 Electricity at Best Besides only on Surface of Conductor, 119 ——Comparing Quantities of, QeA- vanometrically, 299 — — Comparing Quantities of. Stati- cally, lU — — Condensers not Stores of, but of Electric Energy, 322 — Measuring Quantity of. Abso- lutely, 289 Positive and Negative, 85 —— Potential of Conductor Depends partly on Amount of, 119 Quantity of. Defined, 109 Unit of Quantity of, 289 Quantity of, produced by Bub- bing Two Bodies t<^ether, 115 Electrification, Amount of a Body's, 109 — — Exterior, No Force inside Closed Hollow Conductor due to, 99 -^ Object of Subbing Two Bodies together to produce, 115 Electro - Dynamometer, Sie mens', 377. (See also Siemens* Electro-Dynamometer. ElectxomotiTe Foioe of Current Oeneraton, Condenser Method of Comparing, 341 Force, Measuring, 224 Electrophorio Action, Compound Interest Law of. 361—372 Electrophorus, Action of, 360 Bertsoh's Botatory, 361 Description of, 35i6 ^—Ebonite, giving Negative Charges, 359 Ebonite, giviog Positive Charges, 357 Electroscope, Calibrating Gold-Leaf , 354 Condensing, 352 Gold-Leaf , Improved Form of, 94 -— Indicates Potential DifTerenoe, 95 Varnishing Shade of Ordinary Gold Leaf, 97 Electroscopes, Objections to Ordi- nary Gold-Leaf, 96 Element, Simple Voltaic, 209 E. M. F., Meaning of, 204. (See also Electromotive Force.) Enclosiire of Static Electric Appa- ratus in Metallic Case Necessary, 108 Energy, Condensers Stores of Elec- tric, 822 — Produced by Frictional Elec- trical Machine, 352 — Waste of, in Voltmeters with High External Besistance, 422 Equivalent of Heat, Mechanical, 201 Error in Ammeters on Reversing the Current, Testing for, 402 — — in Ammeters Produoea by Ex- ternal Magnetic Disturb- ance, Testing for, 408 ^— in Ammeters Produced by Be- sidual Magnetism, Testing for, 400 -— — in Ammeters Produced by Time, Testing for, 407 —— Testing Voltmeters for Heat- ing, 415 Errors in Voltmeters, Different Kinds of, 407 •~— in Wattmeters^ 445 Examples : i, 12; ii.— vii., 13 ; viii., 14 ; IX., X., 52 ; xi., 53 ; xii. xiii.,55^ xiv.,56; xv., xvi., 57; xvii., 89; xviii, xix., 90; XX., 91; xxi. — xxiv., 142; XXV., 143; xxvi.— xxviii., 155; xxix., 156; XXX.— xxxiii., 158; xxxiv., 182; XXXV.— jxxvii., 163; xxxviii.— xl., 180; xll.— xliii., 201 ; xUv., 202 ; xlv^ 206; xlvi.— xlix., 207; L, li., 227; lii., liii., 228; Uv., 232; Iv.— lvii.,233; iviii.— Ix., 242; Ixi., 243; Ixii.. 247; Uiii., Ixiv., 248; trv., 240; Ixvi., 250; Ixvii.^ Ixix., 252; lxx>, Ixxi., 255; Ixxii, Ixxiii., 256; IxxIt., 259; Ixxv., 260; Ixxvl, 262; Ixxvii., 263; Ixxviii., 264 ; Ixxix., Ixxx., 265 ; Ixxxi., 280 ; Ixxxii.— Ixxxiv., 281; Ixxxv., 294; Ixxxvi., Ixxxvii., 295 ; Ixxx viii., 297 ; Ixxxix. — xci., 298; xcii., 311 ; xciii.— xcv., 312 ; xcvi., xcvii., 313 ; xcviii., xcix., 323; c, 325; d., 326; cii., ail; ciii., 350; civ., 437; cv., cvi., 438; cvii., 439; cviii., cix., 440; ex., cxi«, 443; cxii., cxiii.,44&; cxiv., 446 { cxv., cxvL, 417 ; cxvii., cxviii., 459; cxix., 460; cxx., 471 ; cxri., 473; cxxii., 474 ; cxxiii., 475 Examples showing Difference be- tween Electrio Potential, Density, and (Quantity, 121 Explanation of Electric Sparking, note, 358 External Besistance, Variation of, with Current and Poten- tial Difference at Battery Terminals, 204 Equality of Charges on Two Bodies obtained by Bubbing them together, 115 F PABADAY'S En>eriment on Force ''' in Closed Conductor due to Exterior Electrification, 99 Farad, Definition of the, 307 Fault, Common, in Constructing Ebonite Pillars, 272 Fibre and Pivot Suspensions, 60 Suspension used in Thomson's Marine Gkilvanometer, 60 Field, Uniform Magnetic, 36 Finding Angles from their Tang«ita bv means of Squared Paper, Tangents from their Angles with Squared Paper. 57 the Maximum for an Expre:^ sion by means of Curve, 241 Fixed E. M. F. and Besistance, Cur- rent Developing MpxiquoiB r INDEX. 499 ! I Usefnl Power with Gene- rator with, 448 Fixed Bern stance. Arrangement of Cells nving Mazimnm Useful Power to Condao- tor with, 450 Flat Coil, Direction of Mt^pietic Force prodnced by Cur- rent flowing in, 43 Flemintr'B Standard Daniell's Cell, 412 Flint Glass, Besistance of, 271 Specific Inductive Capacity of, 310 Flow, What is meant by Direction of, of Electric Current, 2 of Electric Current comx>ared with that of Water, 3, 80 Focal Length of Lens, Defimtion of, 456 Force, AttraotiTe, between Two Plane Conductors, For- mida Connecting, with Potential Difference and Distance between them, 87 — Definition of Lines of, 43 — Definition of HorisEontal Com- ponent of Earth's Mag- netic, note, 55 i— Direction of Magnetic, pro- duced by Currant flowing inFhLtCoil,43 —— Electromotive. (Sm Electro- motive Force. ) None Inside Closed Hollow Conductor due to Exterior Electrification. 99 Foster's, Prof. G. C, Simplification of Sine Gkdvanometer, 61 Frictional Electrical Machines, 352 Electrical Maohinee, Con- densers for use witn, 813 Fulfilment of Conditions for Tan- gent Law in Tangent Gal- vanometer, 43 G flALYANIC Cells, 209. (£feea]so ^ Cells.) Jalvanometer. Definition of, 21 Compared with GkdvanoBcope, n<ftet 21 — — Constant of, 278 — Absolute, 57 — Astatic, Advantage of Putting Mirror Outside Coils, 284 -^ Astatic, Definition of, 282 Astatic, Thomson's, 283 — Astatic, Modified Thomson's, 284 -^- Astatic. Mather's, 299 Galvanometer, Astatic, Mndford'i, 105 — Astatic, Damping of Vibra- tions of Needle of, 284, 300 Ballistic, 292 —— Ballistic, Siemens* and Halske's Galvanometer Used as, 292 Dead-Beat, 78 Delicate, 281 Delicate. Importance of being Well Insulated, 286 Delicate, Necessity for Many Convolutions of Wire, 281 Differential, Principle of, 148 Differential Construction of, 14S Differential,I<atimerClark*B,150 Differential, Best B^istance for, 436 Differential, Inferiority of. to Wheatstone'B Bridge, 171 Differential, Mode of Adjust- ing, 150 ——Differential, Use of Shunts with, 183 Direct-Beading, 76 Direot-Beading, Adjustment to make, 75,78,385,389 •^— Large Cmrrent. OalTanometer, Potential IMJferenoe, when it may be Employed, 127 Potential Difference, Testing, 407 — — Proportional, 71 — ' Proportional, with Permanent Magnet Control, 73 Proportional, with Uniform Controlling Field, 72 '—- Quantity, Mather's Simple Form of, 299 Befleeting, 103, 281, 293, 299 Reflecting, Deflection Propor- tional to Current with, 106 Reflecting, Mode of Using Lens with, 105 — — Reflecting, Lamps for, 106 Reflecting, Mirror for, 105 Reflecting, Mather's Form of, 299 Reflecting, Mndford's Form of, 284 Reflecting, Spirit Level for, 285 »— Sine, 62 Sine, Foster's Simplification of, 61 Shielded, 67, 73, 108, 390 Tangent, 36 Tangent, Simple Form of, 27 —— Tangent,Ad1astmentof Coil of, 46 •— Tangent, Best Deflection to Use with, 41 — Tangent, Conditions that a Qalvanometer may be, 36 — Tangent, Conditions of Tan- gent Law Fulfilled in, 43 Tangent, Controlled Only by Earth's Magnetism, Values in Amperes of Deflections of. 55 — ^ Tangent, Proportions of Chan- nel in Bobbin of, when Tangent Law is Most Ac- curately Fulfilled, 51 Tangent, Scale for, 38 Tangent, Sensibilit]r of. Alter- ing, by Removing Needle from Plane of Coil, 52 Tangent, Sensibility of, Al- t*»red by Varying Number of Windings or Diameter of Bobbin, 48 Calibrating, Relatively or Abso- lutely, 22, 27, 39&-400 Calibrating, by Comparison with Tangent Qiilvano- meter, 68 Calibrating, by Sine Method, 64 — — Calibrating, by Sine Method in Higher Parts of Scale, 65 Galvanometer, Calibrating, by Sine Method with Constant Current, 67 Calibrating, by using Known Resistances and Cell of Constant E. M. F., 238 Calibrating, by using Known Resistances and Constant Potoitial Difference, 164 Calibration of. Unaffected by Change in Strength of Poles of Single Needle, 23 Sensibility of, Licreasing, by Diminishing Diameter of Wire used in Winding, 22 Sensibility of. Modes of Vary- ing. 229 Sensibility of. Variation of, with Length of Wire Used in Winding. 418 Sensibility of , Variation of, with Resistance, 416 Sensibility of. Shunting to Diminish, 229 Sensibility of Tangent, Varia- tion of, 48 for Wheatstone's Bridge, Best Arrangement of, and Bat- tery, 171, 487 for Wheatstone*s Bridge, Best Gauge of Wire for. 501 Ghuih Burner, BegeneratiTe, for Qal> Tanometers, 106 Generated in Voltameter Inde- pendent of Shai>e, Size, aud Distance of Plates, 10 Bate of Production in Sul- phuric Acid Voltameter by One Ampere, 12 Gflsesy Dliference of Pressure Com- pared with Difference of Potential, 86, 121 Specific Inductive Capacity of, 310 Gearing, Ammeters and Voltmeters with Macrnifying, 386 Generation of Heathy Eleotric Cur- rent, 192 Generator, Current, Definition of Efficiency of, 451 Current, Measurement of E. M. F. of, 224, 231, 234, 341 Current, Measurement of Re- sistance of, 205, 225. 342 Current, Power Wasted in Heating, 445 Current, Work done by, 202 Current, with Fixed B. M. F. and Besistance, Current Developing Maximum Use- ful Power with, 418 Generators, Current, Forms of, 208. (See also Cell, Batteries.) • German cUlver, Change of Resist- ance of, with Temperature, 100 Silver, Besistanoe of, for Given Length and Diameter, and for Given Length and Weight, 157 — <-> Silver, Resistance of, per Cubic Centimetre and per Cubic Inch. IM Silver, Whv Besistanoe Coils are made of, 160 GiuMS, Flint, Resistance of, 271 Glow Discharge, note, 369 Gk>ld, Change of Resistance of, with Temperature, 160 Electric and Heat Conductivi- ties of, Compared, 150 Resistcuioe of, for Given Length and Diameter, and for Given Length and Weight, 157 Resistance of, per Cubic Centi- metre and per Cubic Inch, 154 Leaf Electroscope, 94 Leaf Electroscope, Calibrating, 354 — Ijeaf Eleotrosoope, Objectiona to Ordinary, 96 Gold-Leaf Electroscope, Varnishing Shade of Oroinaiy, 97 Graduation of Ammeters, Test for Accuracy of, 895 —^ of Canynghame's Ammeter and Voltmeter, 385 of Voltmeters. Testing for Ac- curacy of, 406. (See also Calibrating.) Graphically Beoordiug Besults of Experiments, 30 Beoording Besnlte, Value of, 83 Gravity Control Meters, dQl Darnell's Cell, 212 Grove's Cell, 218 Cell, Chemical Action in, 219 CeU, B. M. F. of, 218 Cell, Besistanoe of, 218 Guard Bing, 89 Tube, 375 Guttaperdia, Besistanoe of, 271 dpecilic Inductive Capacity of, 310 H ~pJBAT, Amount of, per Minute "■■^ Produced by Given Cur- rent flowing through Given Besistanoe, 199 Amount of. Produced per Second in Coil by Constant Carrent, Constancy of, 197 and Electric Conductivities, Comparison of, 158 Conductivity Diminishes more Bapidly than Electric, 159 Evolution of, in Conductor, by Electric Current, 8 Generated by Electric Culr- rent, Amount of, 192 Measuring Current by Bate of Production of, 197 Mechanical Equivalent of, 201 Badiation, Conduction, and Convection of, note, 195 Bate of Production of, in Gal- vanometer Coils, 419 Heating Error in Voltmeters Di- minished by Use of Outside Besistanoe, 421 Error, None in Cardew's Volt- meter, 426 Error, Testing Voltmeters for, 415-422 Gun-ent Generator, Power Wasted in, 415 Property of Current, Practical Uses of, 4 Hermetically Sealing, Definition of, note, 20 High Besistanoes, Measuring, 277 503 PSACnCAL BLBCTBICITT. of Seale, CaKhnOion of» I17 Sine Method, C5 Poiential, Uefinxtum o4 85 Holbnann's Tottameter, 15 Holtx'8 Infiueiioe Electiieia ]f»- chme^ 387 ■ YnleaniBed Indiambber, BeBisteoce of , 271 Componeiit of faith's ICagnetio Force, Defini- tion oi, note, 55 Hone-Power, 201, 443 Hydrogen, Specific IndnctiTe Ga- paci^of,8IO HTpotennse, I>efinition 0^ note, 37 TLLUMINATING Power of Arc -*- Lempi, Measnringr, 454 Power of Are Lamps in any Plane, Measoring, 457 Power of Incandescent Lamps, Measuring, 45S Image, Connection between Motion of, on Plane Scale and Angular Defiection of Mir- ror, 107 Incandescent Lamp, Description of, 454 ■ Lamp, Measuring £fficien<7 of, 452 ^— Lamp, Measuring Illuminating Power of, 452 — ^Lamp, Efficiency and Life of, 458 Indiarubber, Besistance of Hooper's y nlcanised, 271 Specific Inductive Capacity of, 810 Indication of Direction of Current in Magnifying Spring Am- meters andYoltmetors, 389 Induction, Definition of, 97 and Conduction Compared, 97 Self, 174, 427 Inductive Action, 87 Action between Conductors of Different Potentials, 87 Capacity, Specific, 309 Inefficiency of IVictional Electrical Machines, 352 Inertia, Definition of Moment of, note, 78 Infinity Plug, 151 Influence Machine, Adjusting Balls of, to Produce Given Maxi- mum Potential Difference, 372 •~— Machine, Attaching Leyden Jars to Collectors of, 370 Machine, Compound Interest Law of, 8M, 806 Comdettaen for Use with, 313 MacJifne, Distance Spark can be sent between BaJQs of, 370 Machine, Woric done by, 371 Machine, Bertaeh, 361 Machine, Accmnnlating, 361; Holtz's, 867; Nicholson's. 366; Thomson's, 364; Var- ley's, 367; Voss, 867; Wimshnrst) 367 In Parallel, Wires Joined, Defini- tionof, 136 In Series, Wires Joined, DefinitioB <rf,140 Instmctions for Experiments, Spe- cimens of, 4^ Instmments, Commercial, for Mear snring Current, 79, 376 Tnsolating Stand, Construction oL 268 Stems, Coating, with Paraffin Wax or Shell-lac Varnish, 267 Yamish, How to Make, noU^ 268 Insulation, Importance of Grood, and Mode of obtaining, in Delicate Galvanometers, 286 Insulator, Definition of, 9 Insulators, Diminution of Besicct- ance of, with Increase c^ Temperature, 271 Obtainable for Electricity, nut for Heat, 159 Table of Besistances of, 271 • Telegraph, 274 Testing, during Manufacture, 275 International Electrical Congress, Unit of Besistance Adopted by, 140. 141 Interpolation of Besults by Means of Curve, 34 Invariable Absolute Calibration, Gfalvanometers with, 57 Iron Box, Partial Magnetic Screen, 101 Change of Besistance of, with Temperature, 160 Electric and Heat Conductivi- ties of. Compared, 159 Besistance, of for Given Lengtb and Diameter, and for Given Leng^ and Weight, 157 Besistance of, per Cubic Centi- metre, and per Cubic Inch, 154 Cores, Use of, in Galvanoi tars, 73 INDEX. 503 Iron Magnetiflod by Eleotrlo rmtfS BesiBtanoe Coils, 162 Cor- TAB, "Lejden, 314. (Sm also L^- ^ den Jar.) Used for Darnell's Cell, 210 Joints, Lap and Bntt, 79 Jonle, Definition of the, 461 Joule's Mechanical Eqaivalent of Heat, 201 XTEMFE'S ConstantTotalCorrent -'^ Shunts, 257 Key, Bridge, 174 Charge and Discharge, 820 Charge and Discharge, Simple Form of, 343 — — Charge and Discharge, Various Modes of Connecting, with Condenser, Battery, and Gkilyanometer, 320—322 -— Make and Break, Simple Form of, 19 Ping. Description of, 139 Eirchhoff's First Law, M4 Second Iiaw, 464 T ALANDE Chaperon Cell, 210 ■*^ Lamps, Description of Arc and Incandescent, 454. {See also Arc, Incandescent.) Lamps Used with Beflecting Galva- nometer, 105 Lap Joint, 79 Large Potential Differences, Pro- duction of, 351 Latimer Chirk's Cell, 410 Clark's Cell, Constancy of E. M. F. of, 411 Clark's Cell, E. M. F. of, 411 Clark's Cell, Temperature Va- riation of E. M. F. of, 411 Clark's Differential Galvanome- ter, 150 Law connecting Two Sets of Facts Determined by means of Curve, 35 of Differential Galvanometer, 149, 183 Experimental Proof of Ohm's, 130 Kirchhoff's First, 464 Kirchhoff's Second, 464 Ohm's, ISO Tangent, Fulfilment of Condi- tions for, in Tangent Gal- vanometer, 48 Law, Tangent, When True, 41 Sine, When True, 61 of Wheatstone's Bridge, 167 Laws of Surfoce Leakage ana Leak- age through uie Mass, 270 Lead, Change of Besistance of, with Temperature, 160 — ^ Electric and Heat Conducti- vities of. Compared, 150 Besistance of, for Given Length and Diameter, and for Given Length and Weight, 157 Besistance of, per Cubic Centi- metre, and per Cubic Inch, 154 Leakage, Dependence of Bate of Loss of Charge from, on Dielectric Only, 346 Surface, 266 Surface, Law of, 270 through the Mass, 266 through the Mass, Law of, 270 Leclanch^ Cell, 220 Cell, Chemical Action of, 221 CeU, E.M.F. of,222 Legal Ohms and B. A. Units, Equa- tion Connecting, 142 Unit of Besistance, 140 Length, Variation of Besistance with, 143 Lens, Definition of Focal Length of, 456 —— Mode of Using, with Beflecting Galvanometer, 104, 105 Levels, Spirit, for Beflecting Gal- vanometer, 285 Lejden Jar, Attaching, to Collecting Combs of Electrical Ma- chines, 370 — '- Jar, Construction of, 314 Jars, Battery of, 317 Life of Incandescent Lamps, 458 Light, Measuring Efficiency of Elec- tric, 452 Measuring Illuminating Power of Electric, 452 Lines of Force, Definition of, 43 Liquid and Wire Besistances, Com- parison of Use of, 194 Decomposed by Electric Cur- rent, 3 Saturation of, twte, 411 Super-saturation of, noUf 411 Liquids, Difference of Level in. Com- pared with Difference of Potential, 86 Local Action in Cell, 217 Action in Daniell's Cell, How to Prevent, 217 504 PRACTICAL ELECTBICITT Lockwood Cell, 218 Logarithmic Deorement, 296 Decremeut, Determination of, when Damping is Very Slight, 297 Lord JUtyleiflrh, Silver Voltameter uBea hy, 11 M llf ACHINES, Electrical, Adjnat- **"• ing Balls to Produce Given Potential Difference, 872 Electrical, AttHchiog Leyden Jars to Collectors of. 370 — — Electrical, Condensers for Use with, 313 Electricat, Frictional, 852 Influence, Bertsch's, 861 ~-^- Influence, Accumulating, 861 ; Holtz, 867; NichoUon's, 366; ThomsonV, 864 J Var- ley's, 367; Voss, 8j7; Wimshurst, 867 —— Influence, Accumulating, Con- densers for Use with, 813 "^ Influence, Accumulating, Com- pound Interest Law of, H61, 866 Influence, Accumulating, Work done by, 871 Magnet, Connection between Poles of, and Diioction of Cur- rent round, 17 — Definition of North-Seeking End of, note, 16 Deflected by Current, 8 llectro. (See ElectroMagnet. M5 M aximom Potential DiflTerenoe of Electrical Machine, Deter- Diination of, 372 *—— Useful Power, Current tbat Develops, 448 —— Useful Power in (Generator with Fixed E.M.F. and BesistaDoe, Conrent that Develope, 448 Measuring Arc Light, Effidenoj of, 455 — Arc Light, lUuminating Power of. in any Plane, 457 — > Arc Light, Illuminating Power of, How to Oyeroome Dif- ference in Colour between it and Candle when, 457 — Effioiraicyof Electric Light, 458 — Efficiency of Incandescent Light, 452 Current, Alternating, 196 ——Current, Commercial Instru- ments for, 79, 376 — Current by Bate of Production of Heat, 197 Current with Siemens' Dynar mometer, 379 — Small Curreots, Disadyantage of nsiuff Yoltameters f or,20 —— Strength of Current, 4 — Distritmtion of Magnetism in Permanent Magnet, 24 Electric Density by means of Proof Plane, 117 — Electromotiye Force of Cur- rent Generators, 224, 2?1, 234,341. (Sm also Electro- motiye Force.) Potential DifTerence by Weigh- ing, 88 — Potential Differences, Alter- nating, 426 Potential Differences. Static and Current Methods of. Compared, 125 Power, 442 Resistance of Batteries, 205, 225 Resistance of Batteries using Known Besistances, 226 — — Besistanoe of Batteries using Known Besistances ana Shunt, 226 — Besistanoe of Current Gener- ator, Condenser Mtthod of.S42 — — Besistanoe by Bate of Loss of Charge, 314 ^— Resistance by Bate of Loss of Charge, Gkdyanomeirio Method of, 348 — X- Besistanoe Contaiuiug E.M.F., 409 Measuring Besistanoe during P« sage of Strong Current, 187 High Resistances, 277 Speciflc Inductive Capacity, —— Quantity of Electricity, 111, 289,299 MeasuremAnt Absolute, of Capa- city, 827 of Po e.itial Compared with Measurement of Tempera- ture, 85 Mechanical Equivalent of Heat, 201 Meidinger GeU, 212 Mercury, Change of Besistanoe of, with Temperature, 100 Resistance of, for Giren Lenrth and Diameter, and for Given Length and Weight, 157 — Resistance of, per Cubic Centi- metre, and per Cubic Inch, 154 Meridian, Definition of Plane of Magnetic, note, 45 Metal having Least Change of Re- sistance with Tempera- ture, 160 Metals, Change of Resistance of, with Temperature, 160 < Electric and Heat Conducti- vities of. Compared, 159 ^•^ Resistance of, for Given Length and Diameter, or for Given Length and Weight, 156 Resistance of, per Cubic Centi- metre, ana per Cubic Inch, 153 Metallic Case, Necessary Enclosure of Electric Apparatus in. • 108 * -^ Meters, Electro-Magnetic Control, —^Electro-Magnetic Control, Cronipton and Kapp's, SK3 -«» Electro-Magnetic Control, Pa- terson and Cooper's, ^ Electro-Magnetic Control, Ad- vantages of, 394 — — Electro - Magnetic Control, Disadvantages of, 394 Gravity Control, 391 Spring Control, 377 Spring Control, Cunynghame'f , sen I Magnifying, 386; Siemens', 377 Meters. (S«e also Ammeter, Dyna* mometer. Galvanometer, Photometer. Voltmeter, Wattmeter.) Metre Bridge, 168 Mica, Reaistanoe of, 271 506 PRACTICAL BLECTBICrry. Mica, Speoiflo Indaotive Capacity of, 310 ICicrometer Sozew, Description of, note. 24 Minotto'B Cell. 211 Mirror, Angalar Motion of. Half that of Beflected Sajr, 106 -^Connection between Angnlar Deflection of, and Motion of Image on a Plane Scale, 107 ——in Galvanometer, Use of, to Avoid Parallax, 28 for Reflecting OalTanometer,105 Moment of Couple, Definition of, note, 283 of Inertia. Definition of, note, 78 Motion, Angular, of Refiected Bay, 106 of Image on Plane Scale, Con- nection between, and Angu- lar Deflection of Mirror, 107 of Magnet produced bj Uni- form Magnetic Field, 380 Multiples of Ohm, Conatmction of, 145 Multiplying Power of Shunt, 178 Power of Shunt uaed in Measuring a Discharge, 340 N 'M'APIERIAN Logarithmic De- -^^ crement, 296 Negative Charges, Ebonite Electro- phorus Arranged to Give, 358 Electricity, 85 Network, Currents in, 462 Nicholson's Revolving Doubler, 366 Nickel, Resistance of, per Cubic Centimetre, and per Cubic Inch, 154 North-seeking end of Magnet, Defi- nition of, note, 16 Nought, Potential of Earth Arbi- trarily taken as, 84 Null Methods, Meaning of, 236 O r)HM, 89, 140, 141 ^^ Construction of Multiples of, 145 — — Definition of ]>efl»l, 140 Only Electrical Unit yet Legal- ised, 140 Ohmmeter, Description of, 190 Ohms, L^al, and B. A. Units, Equa- tions connecting, 142 Wires having Resistance of abont Ten, 143 Ohm's Law, 130 Law, Experimental Proof of, ISO Oleflant €hu3. Specific Inductive Capacity of, 310 PARAFFIN WAX, Coating In- -^ sulating Stems with, 267 Wax, How to Prevent Over- heating when Melting, note, 267 Wax, Resistance of, 271 — — Wax, Specific ^ductive Capa- city of, 310 Parallax, Definition of, note, 28 Mirror Used in Galvanometer to Avoid, 28 ParsJlel. Cells in. Figure of, 239 Cells in. Symbolical Repre- sentation of, 240 Circuit, Wires Joined in, 136 Circuit, Independence of Cur> rents in, 260 E. M. F. of Cells in, 241 Resistance, 179 Patersonand Cooper's Electro-Mag- netic Control Meters, 393 P. D., Meaning of, 230 Periodic Time of Vibration, Defini- tion of, 291 Permanent Magnet, Proportional Galvanometers Controlled by, 73 Magnet, Measurement of Dis- tribution of Magnetism in, 24 Magnet Meters, 69 Magnet Met^, Advantages of, 78 Magnet Meters, Direct-Read- ing, 76 Magnet Meters, Disadvantage of, 376 Magnet Meters, Proportional, 71 Photometer, Dispersion, 454 Rumford's, 452 Pivot and Fibre Suspensions, 60 Plane of Magnetic Meridian, Defini- tion of, note, 45 Proof, 116 Platinoid, 160 Resistance of, 161 Resistance, Coils of, 161 Platinum, Electric and Heat Con- ductivities of. Compared, 158 Resistance of, for Given Length and Diameter, and for Given Length and Weightb lfi7 INDEX 507 Platinum, Befdstanoe of, per Oubio Centimetre, and per Cnbic Inch, 154 Silver Alloy, Change of Becdst- anoe of, with Temperature, 160 — — Silver Alloy, BesiBtanoe of, for Given ijenffth and Dia- meter, and for Qiven Length and Weight, 157 Silver AUoy, Besistanoe of per Cubic CentinuBtre, and per Cubic Inch, IM Plug, Infinity, 151 Key, Description of, 188 Becnstonoe Soxes, Construction of, 151 Poggend(»rff'8 Method of Compar- ing £. M. Fs., 234 Method, Use of, for Calibrating Yoltmeters, 413 Polarisation of Daniell's Cell, 216 of Latimer Clark's Cell, 411 Poles of Magnet, Connection be- tween, and Direction of Curroit round Magnet, 17 of Magnets, Positions of, 23 •Portable Electrometer, 93 —— Qalvanometer with Approxi- mate Absolute Calibration, 69 Positive Electricity, 85 Potential, 85 Potash Bichromate CelL 222 Bichromate Cell, Cnemical Ac- tion in, 223 — — Bichromate Cell, Composition of Liquid for, 222 Bichromate Cell, E. M. F. Potential Differenoe Beqnired to Produce Spark between Two MetalUc Balls, 370 1^— Differenoe, Static and Cunent Method of Measuring, Compared, 125 <— - Differenoe, Sub-diridinff into Known Fractions, 2^ —— Difference. Variation of, at Bat* tery Terminals, with Varia- tion of Current, 204 DlfferenoeL Variation of, with Resistance of Oiven Volt- meter to Produce Given Deflection, 419 — — Higher, and Lower, Positive, and Negative, Definition of, 85 •— Increasing Senaibility of Weight Electrometer by Using Auxiliary High, 91 —-— Inside Closed Conductor, 96 "»> Measurement of, Compared with Measuremeutof Tem- perature, 85 — — of ifarth Arbitrarily taken as Nought, 84 Uniform on Conductor, 86 Uniform in Conductor, 98 Power, Arrangement of Cells Giv- ing Maximum Useful, to Conductor of Fixed Resist- ance, 450 — ~ Current Developing Maximum Useful, with Generator of Fixed E. M. F. and Resist- ance, 448 DefipHion of, 441 Distribution of, in Circuit, 445 E. M. F. used by Deprez in Transmitting, 87 Miles, 452 Horse, 201, 443 Measurement of, 442 Unit of. 442 -^ Utilisea in Circuit Outside Ge- nerator, 445 Wasted in Heating Generator, 416 Preparation of Varley's Carbonised Cloth, 397 Pressure, Difference of, in Gases, Compared with Difference of Potential, 86 — ~ of Gas Compared with Poten- tial of Conductor, 121 — — of Water, Difference of, in Pipe Compared with Difference of Potentials, 81 Proof of Ohm's Law, Experimental, 130 Proof-plane, 116 Proof-phine, Measuring Electrjfl Density by means of, 117 Properties of Eleclxic Current, 3 of Electric Current, Practical Uses of, 4 Proportional Coils of Wheatstone'a Bridge, 172 Galvanometer, 71, 75, 108, 389 Proportions of Channel in Bobbin of Tangent Galvanometer, when Tangent Law is Most Accurately Fulfilled, 51 Q QUADRANT Electrometer, Thom- son's, 03 Electrometer, Edelmann's Mo- dification of Thomson's, 130 Electrometer, Edelmann's Mo- dification of Tuomson's, Defects in, 134 Electrometer, Edelmann's Mo- dification of. Dry Pile for. 133,372 Electrometer, Edelmann's Mo- dification of. Needle for, 132 Electrometer, Formula for, 134 Quantities of Electricity, Compari- son of, HI, 299 Quantity of Electricity, Definition of, 109. (See also Charge.) of Electricity, Unit of, 289 of Electricity Produced by Rubbing Two Bodies To- gether, 113 Potential, Density, Examples showing Difference be- tween, 121 Unit of, 289 R T> ADIATION of Heat, Explanation -'-*' of, note, 195 Rate of Loss of Charge, Measuring Resistance by, 344 of Production of Heat in Gal- vanometer Coils^ 419 of Production of Bleat, Mea- suring Current by, 197 Ratio of Potential Differenoe to Current Constant with Given Conductor, 130 of Potential Difference to Cur. rent is the Resistance, 130 of Sensibilities of Commuta- tor Ammeter in Parallel ^d in Series, 431 1%'DEX. 509 Ratio of Sensibilities of Yoltmeter in Parallel and in Series, 433 Eajleigb, Lord, Silver Voltameter Used by, U, 895 — Lord, Temperature Variation of E. M. F. of Clark's Cell Determined by, 411 Becordingr Besults of Experiments araphically, 30 — Results of Experiments Gra- phically, Value of Curves for, 33 Reflected Bay, Angpilar Motion of ,106 Reflecting Galvanometer, 103, 281, 293, 299. (See also Galva- nometer, Reflecting.) — — Ghdvanomet^, Different Ways of Forming Image with, 105 Gkdvanometer, Lamp Used with, 106 Galvanometer, Modes of Using Lens with, 105 — — Galvanometer, Spirit Level for, 285 Relative Calibration of Qalvano- meter. Meaning of, 22 Relatively Calibrating Galvanome- ters, 27 Replenisher, Thomson's, 364 Representation of Batteries, Sym- boUcal, 173, 240 Residual Magnetism, Definition of not0, 388 — Magnetism, Testing Ammeters for, 400 Resin, Specific Liductive Capacity of, 310 Resistance, 9, 129 — — Amount of Heat produced per Minute by Given Current flowing through Given, 199 »— and Current, Variation of Mag- netic Effect of Bobbm with, 418 ^-— Api>arent Increase of, in GkJ- vonometer, Due to Damp- ing, 349 of Battery, Measuring, 205, 225, 342 —— Best, for Differential Galvano- meter, 436 — — Best, for Galvanometer in Sim- ple Cirouit, 485 ^— Best, for Galvanometer of Wheatstone's Bridge, 172, 466 — — Best, for Coils of Wheatstone's Bridge, 171 o— Best, to Give to Galvanometer, 435 — — Box, Description of, 28 — - Bo9(, Conatmotion of Plug, 161 J Resistance Box, Construction of SUdiug. 186 Box used in Duplex Tel^^raphy, 187 Resistances, Calibrating (Galvano- meter by Using Known, and Constant Potential Differ- ence, 164 Calibrating Galvanometer by Using Known, and Cell of Constant E. M. F., 238 Change of, with Temperature, Riesults of Matthiessen'fi Experiments on, 160 -^— Comparing, 136 Comparing, Differential Galva^ nometer Method of, 148 Comparinfr, Potential Differ- enoe Method of, 140 — — Comparing, Simple Substitu- tion Method of, 138 Comparing, IVheatstone'a Bridge Method of, 166 Comparing Use of Liquid and Wire, 194 Resistance Containing E.M. F., Measuring, 469 Coils, 28, 145, 151, 153, 159, 163 Coils, Accurate Standard, 162 Coils, Construction of, 145 Coils Heating with Strong Cur- rent, 192 Coils, German Silver, 160 Coils, Iron, 162 Coils, Platinoid, 161 Coils, Platinum-Silver Alloy,160 Coils, Materials used in, 150 Coils, Modes of Winding, 163 Colls, Temperature Variation oM58 Increase of, by Self-induction. 427 of Current Generator, Conden- ser Method of Measuring, 342 of Daniell's Cell, 211 of Grove's Cell, 218 of Insulators, Diminution o^ with Increase of Tempera- ture, 271 of Insulators, Measuring, 275 of Insulators, Tftble of, 271 -^ of Insulator to Sparldng, 311, 370, note, 358 .Law of Variation of, with Tem- perature, 152 Measuring, by Bate of Loss of Charge, 844, 31S Measuring, Containing E.M.F., 469 Measuring, during Passage ol Strong Current, 187 510 PBAOTIOAL ELBOTRIOITT. Hiflrh,277 jtCh — — Metal lukTiiig Least Change of, with Tempetatue, 160 PaiaUel. 179 of GalTanometer and Shunt Combined, 178 ^— of Metals for Given Lei^h and Diameter, or for Given Length and Weight, 156 -^ of Metals per Cnbic Cratimetre, and per Cable Inch, 153 of Platinoid, 161 per Cable Centimetre, and per Cubic Inch Compared, 348 Proportional to Katio of Poten- tial IHiferenoe to Current, 130 ——should be High in Potential Difference Oalyanometers; 137 — should be Low in Current Gal- ▼anometfflrs, 136 Unit of, British Association, 141 Unit of. Legal, 140 Unit of, Siemens', 142 Variation of, with Length, 143 >— Variation of, with Material, 146 *— Variation of, with Sectional Area, 146 — Variation oi, with Temperature, 147,152 Variation of Sensibility of Gal- vanometer with, 416 Variation of Sensibility of Voltmeter with, 407, 418 Voltmeters with Outside, 421 Results of Experiments Corrected by Drawing Curves, 34 ^— of Experiments, Graphically Recording, 30 — of Experiments, Value of Curires in Graphically Re- ccMrding, 33 Interpolation of, from Curve, 34 Retardation, Definition of, 331 Reversing Current without Alter- ing its Value. 47 Revolving Doubler, Nicholson's, 366 Rhig, Goard, 89 Roes Cell, 210 Rotatory Electrophoms, 361 Rough ExjMriments, Candles to use in the place of Standard Candles for, 452 Rubbing Two Bodies together. Quantity of Electricity Produced by, 113 -^Two Bodies together to Pro- duce Electrification, Ob- ject of, 115 — Two Bodies together, Equalily of Charges Obtained by, 115 Romford's Photometer, 458 Rymer Jones' Constant Total Cur- rent Shunts, 2S9 8 CATURATION, Magnetic, 388 ^ of Liquid, Definition of, 411 Safety Arrangement with Com- mutator Ammeter, 432 Scale, Connection between Motion of Image on Plane, and Angular Deflection of Mir- ror, 107 for Tangent Qalvanomet«r, 39 Mode of Making Tangeot, 39 Scales, Accuracy of Readings with Degree and Tangent Com- pared, 40 Screen. Magnetic, Thick Iron Bos* 101 Screw, Micrometer, Description of, note, 24 Sealing Hermetically, Definition of, nota, 20 ^— up One End of Cable when under Test, 268 Seoondairy Batteries, Small Litemal Resistance of. 206, 261 Batteries, Use of, in Electrie Lighting. 261 Sectional Area, Variation of Resist- ance with, 146 Self-InduoUon, 174, 427 Induction, Sxnall, in Cardew's Voltmeter. 427 Sensibilities of Commutator Am- meter, Ratio of, in Parallel and in Series, 431 — of Commutator Voltmeter, Ratio of, in Parallel and in Series, 433 Sensibility, Adjustment for, in Magnifying Spring Am- meters and Voltmeters, 889 of Galvanometer, Variation of, 21,48,229 Gl Galvanometer, Variation of, with Length of Wire used in Winding, 418 — — of Galvanometer, Variation oi, with Resistance, 416 of Tangent Galvanometer Al- tered by Removing Needle from Plane of Coil, 52 ——of Tangent Galvanometer Al- tered by Varying Number of Windings or Diameter of Bobbin, 48 ot Voltmeters, Variation of, with Change of Resistanoob 407,418 INDBZ. 511 Bensibilify of Wheatstone's Bridge, Conditions affec(3ng,171,406 — — of Wheatstona's Bridge, Mode of Increasing, 168 of We^rllt Electrometer, In- creasing, by Using Anxili- Bxj High Potential, 91 — fflinntmg Qalvanometer to Diminish. 229 — ~ Testing Ammeters for Perma- nent Altepttion of, 407 Two Degrees of, in Commutator Ammeter and Voltmeter, 427 Series, E. M. F. of Cells in, 241 Cells in. Figure of, 239 Cells in. Symbolical Repre- sentation of, 240 — — Wires Joined in, 140 Several Currents Meeting at a Point, Law Connecting, 464 Shell-lac, Beaistance of, 271 ——•loo Specific Indactive Capa- city of, 310 —. .lac vamish. Coating Insu- lating Stems with, 267 — — -lao Varnish, Preparation of, fu>e«,268 Shielded, Dead-Beat, Direct-Bead- ing Qalvanometers, Advan- tages of, 78 Shielding Galvanometers from Ex- traneous Magnetic Disturb- ance, 57, 73, 108, 390 Short-Circnited, Definition of, 217 Shunts, 50, 177, 183, 253 Shunt Box, Construction of, 181 Shunts, Constant Total Current, 257 Shuntand Qalvanometer^Combined Besislanoe of, 178 — Increase of Total Current pro- duoed by Use of, 183, 2d3 ^— Measuring Besistanoes of Bat- teries by means of, 226 Multiplying Power of, 178 — Multiplying Power of, when Used In Measuring Dis- charge, 349 Shunts, Use of, with Differential Galvanometer, 188 Shunt, Use of, with Wheatstone's Bridge, 176 Shuntii^ Battery only while Charg- ing Condenser, Arrange- ment for, 843 -~— Galvanometer to make it Less Sensitive. 229 Siemens' Electro-Dynamometer, 377 ——Electro-Dynamometer, Advan- tages of, 380 <to— Electro-Dynamometer, Disad- irimtag«s of , 381 Siemens' Electro - Dynamometer, Measuring Current with, 379 Electro-Dynamometer as Stan- dard Jjxstmment, 382 Siemens' Unit of Besistanoe, 142 Silver, Change of Besistance of, with Temperature, 160 Electric and Heat Conductivi ties of. Compelled, 159 Besistance of, for Given Length and Diameter, and for Given Length and Weurht, 157 Besistance of, per Cubic Centi- metre, and per Cubic Inch, 154 Chloride Battery of De la Bue and Hugo Mailer, 314 Voltameter, Description of, noU.JLl, 395 — — Voltameter, Precautions in Using, note, 11 — Voltametor, Use in Calibrating Ammeters, 395—400 Voltameter Used by Lord Bayleigh, 11, 395 — Voltameter, Weight of Silver Deposited on Plate of, per Second, by One Ampere, 11 Similarly Chanred Bodies ; Beason they Fly from One An- other, 840 Simple Substitution Method of Comparing Besistanoes, 138 Voltaic Element, 209 Sine, Definition of, not», 38 Galvanometer, 62 Qalvanometer. Potaitiil I>inTaHe Bcqnind to PndnoE.betwevPohrt FotolU DUmwM B«|Dlnd to Tndaea, tut km Two Brhskal Co^leaMr, C^uitT of. Biiiiir T iiiiihfiii ■■■■! 11^ niliiiii BpMtilc Induttia Ca|»dtj, I>■■B^ Inductin CanettT o( SoUd* Ukd lAqtMM, 31A iBdncUreCipHi^, pcriimt*. ea — OoBtroI Kitsri, CBBTag. — Oootnl Xeton, Hksaidi^, SM. (&• ■!» K>«iiitTtn« 8|>rfBc AmmMar md Volt- 33 P*pn; Bslectioii of Soluble ^niti on, 31 Paper. Uw ol, 80 •■ — Fmper, Tiliw, to nud Ancles fmH theit 'biigenta. 56 Pkper, Uciiw, to Find Tangenta iiithriiA3glea,E7 ' — Dulsll-i Cell. E. M, F. ol, 4U Diwlell'i CelL neBdnTi. 413 VdtBMta.^ BUtio ud Cnireat Methods of KeMorhK Polentlsl DU- CareiHKfl Coupsred, 18S • — Electric Appanitai, Neceaaeiy Enetonro of, In Hetallio Cue, !«§ Btstloil Vetliod of Compuli« CapMitlex, 310 Stami, Canting Innilitlne, with Fuiffln Wu oi fihell-lu StoiEga Calli, ^ull lotenul B*. ■taUaca ol, IQ CbcBkal FiDpntr, 10 o<Kk«tn>-]bBHit, Iaw 01, ^m Con ie Oiirtitlr Xiw- rf Folca oi Sa^ Haedle d OslnMtaeter, CatOntioa Unnffectodbr, 2S SBiUnc INftuKO, Mtnttfan <^ Strong Cnirent. HeanriBg Bcaist. . . ..__.... JMecUcm to OrdinuT Fom el, IS AddTaUsaetet.Tahnne ot Om luccd io, per Becond^ sld^oltu Add f oltamelar.Weiclit ol Qu produced in, per Second, hj one AmpoB, !S er-Htiimtton or Liqnid, Delink Uon ol, luti, 411 :ueLakue^»8 Lakige, law cl,J7D ot COBdD«eor, Electricity at '■-it BeiddecOnlTon^llS . Fliffe, lined in ^lotii' ■OD*! KuiDe OalniBonia. ter.m cm, Fifotand Fibre. Co^ rpABLE ol ElnHria und HeM ol fioidBtartoeB i>f iDBolaton, INDEX. 513 Table of Resistances of Metals per Cubic Centimetre, and per Cubic Inch, 154 —— of Si>ecific Inductive Capaci- ties, 310 of Temperature Variation of Resistance, IGO showing Potential, Density, and Qudiitity of Electricity un ConductKM.* in Different Conditions, 123 showiog Variation of External Resistance, Current, and Potential Difference at Battery Terminals, 205 Tangent of Angle of Deflection Proportional to Current in Tangent Qalyanometer, 43 — Definition of, no'e, 37 — and Degree Scales, Accuracy of Readings Compared, 40 Galvanometer, 36 »— Galvanometer, Alteration of Sensibility of, by Altering Position of Needle, 51 Galvanometer, Adjustment of Coil of, 46 — — GMvanometer, Best Deflection to Use with, 41 Galvanometer, Calibration of Galvanometer by Direct Comp:)rison with, 58 •— Galvanometer, Conditions to be Fultilled in, 36 — — Galvanometer, Controlled Only by the Earth's Magnetism, Values in Amperes of De- flections of, 55 ^— Galvanometer, Fulfilment of Conditions for Tangent Law in, 43 — — Galvanometer, Proportions of Channel in Bobbin of , when Tangent Law is Most Ac- curately Fulfilled, 51 Galvanometer, Scale for, 39 — Galvanometer, Simple Form of, 27 Law, How Conditions of, are Fulfilled in Tangent Gal- vanometers, 43 Law, When True, 41 Scale, Mode of Making 88 Tangents, Finding Angles irom, by means of Squared Paper, 56 Telegraph Insulators, 274 Insulators. Testing during Manufacture, 275 Telegraphy, Resistance Boxes used in Duplex, 187 Telephone, Description of the Bell, 336 H H Temperature, Change of Resistance with, Results of Matthies- sen's Experiments on, 160 Curve, Cooling Correction of Observed Hiae of, 196 Diminution of Resistance of Insulators with Increase of, 271 Equation connecting Variation of Resistance of Metals with, 153 Law of Variation of Resistance with, 152 Measurement of, Compared with Measurement of Po- tential, 85 Variation of E, M. F. of Lati- mer Clark's Cell, 411 Variation of Resistance with, 147 Testing Ammeters, 394 Ammeters for Accuracy of Graduation, 395 Ammeterd for Error on Re- versing the Current, 402 — • Ammeters for Error Produced by External Magnetic Dis* turbance, 403 — — Ammeters for the Permanent Alteration of Sensibility, 407 Ammeters for Residual Mag- netism, 400 —^ Cables, Sealing up One End while. 268 Insulators during Manufao- ture, 276 Voltmeters, 407 Voltmeters for Accuracy of Graduation, 408 Voltmeters for Heating Error, 415 Testing. (See also Comparing, Mea- suring.) Thompson's, Prof. 53 — — Leyden Jar, 815 Marine Galvanometer, 103 514 PRACTICAL ELECTRICnr. ThomMOm'n, Sir William, Marine Oalnmometer, Fibre Sna- penaion need in, 60 ^—Marine Galvanometer, Shields iag, from Magnetic Dia- tarbanc% 108 — - Beflectin< Oalvanometer, 283 Beplenisher, 364 Time ffiae of Temperature due to Paaaage of Current, 195 Tin, Change of Besistance of, with Temperature, 160 — — Electric and Heat Conductiri- ties of. Compared, 150 — »- Seaistanoe of , for Qiven Length and Diameter, and for Given Length audWeight, 167 — — Beaistanoe of, per Cubic Cen- timetre, and per Cubic Inch, 154 U TTNITOBM Controlling Field, ^ Proportional*(Hlvanometer with, 72 Magnetic Field,I>eflnition of, 96 Magnetic Field, Motion of Ma^et Proauoed in, 300 Potential on Conductor, 86 Unit of Capacity, 907, —— of Current, 11 of Density, 117 of Potential Difference, 89, 141 of Power. 442 of Quantity, 289 of Keaistance, B.A., 141 of Besiatance, British Associa- tion, 141 •—— of Besistance, Legal, 140 of Besiatanoe, Sieiuena', 142 of Besistance, B. A. and J^egal, Comj^ared, 142 Units. Selection of, Suitable en. Squared Paper, 92 "yALUES in Amperes of Defleo- ^ tions of Tangent Galvsno- meter Controlled OnW by Earth's Magnetism, 55 Variable Besistance in Voltmeters caused by Self-induction vdth Alternating Potential Diiferences, 427 Variation of Capacity of Condenser with Area of, and Distance between, its Coatings, 903 — of External Besistance, Cur- rent, and Potential Dif- fersnoe at Battery Term!* nals, 204 Variation of Maxnetic Effect of Bobbin with Currmt and Besistance, 418 '—— of Besistance with Length, 143 '-— of Besistance with Material, 146 of Besistance with Sectional Area. 146 -^of Besistance with Tempera- ture, 147 of Besistance with Tempera- ture, Law of, 152 — — oi Sensibility of any Galvano- meter by Altering Di»- meter of Wire, 22 -— of Sensibility of any Galvano- meter with Length of Wire used in Winding, 418 — of Sensibility of any Galvano- meter by fehuntrng, 229 — — of Sensibility of Galvanometer with its Besistance, 416 of Sensibility of Tangent Gal- vanometer, 48 of Sensibility of Voltmeterwith Chanee of its Besistance, 407,418 Produced in Total Current by Shunting Portion of Circuit, 259 — — with Temperature of E. M. F. of Daniell's Cell, 211 — — with Temi>erature of E. M. F. of Latimer Churk's CeU. 411 Varley's Accumulating Influence Machine, 367 Varnish, Coating Insulating Stems with Shell-lac, 267 i How to make Insulating, nots. Varnishing Shade of Ordinary Gold- Leaf Electroscope 97 Varying Potential Differeaoe in Known Batio, 278, 954 Vibration, Definition of Periodio Time of, 291 Voltaic Element, 209 Voltameter cannot Measure Alter- nating Current, 198 —— Copper, Description of, 6, 11. (Se9 also Copper Volta- meter.) Hoffmann's, 15 Silver, Used by LordBayleigh, 11,995 Sulphuric Add, Construction of. 18 Sulphuric Acid, Description of, i Sulphuric Acid. Volume of Qaa produced m, per Beconrt, by One Ampere, 12 INDEX. 515 Voltameter, Sulphnric Acid, Weight of Qts produced in, per 8(>c»nd, Dy One Ampere, 22 Zinc. {8e0 Zinc Voltameter.) Voltameters, Objections to osnal Mode of Constracting, 18 •— ^ and Qalvanometers, Belative AdvHntKges of, 20 ——Direction of Current in Acid, Copper, and Zinc, 15 — — Disadvantage of, 20 ludependenceof Qss Generated and of Metal Deposited of 8liai>e, Sise, and Distance Apart of Plates, 10 ^>— Precautions in Usinig, nott, 11 -^— Silver, note, 11 — Silver, Use of, in Calibrating Ammeters, S85— 400 ——'Weights of Metals Deposited on Plates of, per Second, by One Ampere, 11 — Why Only Used in Measuring Large Currents, 20 Volt, The, 86 Practical Definition of the, Ul Provisional Definition of the, 80 Voltmeters, 128, 376 Voltmeter, Cardew's Latest Form of, 423 — > Cardew's, Advanti^es of, 426 — Cardew's, Arranged for Measur- mg ijarge Potential Dif- ferences, 425 Csrdew's, Diameter of Wire Used in, 423 Tardew's, Disadvantage of, 427 — — Cardew's, Length of Wire Used in Latest Form of, 423 — Cardew's. No Heating isirror in, 426 — Oaardew'B. Self-Liduction Small in. 427 — Commutator, 427 — ^ Commutator, Calibrating, 433 Cnnyngtiame's, 382 ^— Cnnynghame's, Advantages and Disadvantages of, 3^ Cnnynghame's, Graduation of, — - Electro-Magnetic Control, 392 — Electro- Magnetic Coutrol, Crompton and Kapp's, 392 — Electro-Magnetic Control, Patersdn and Cooper's, 393 ^— Electro-Megrnetic Control, Ad- vantage and Disadvantage of 394 — Gravity Control, 8B1 Voltmeteiv Gravity Control. Ad- vantages of, 391 — Ghravity Control, Disadvantages of, 394 Magnifying Spring, 386 Magrnifying Sprmsr, Adjust- ment for Sensibility in, 389 Magnifying Spring, Advantaisea of. 390 Magnifying Spring, Best Law of Gauge of Wire for Coils of, 421 —— Magnifying Spring, Disadvan- tage of, 391 — Magnifying Spring, Lidicatlon of Direction of Current in, 389 Permanent Magnet, 69 Permanent Magnet, Advantages of, 78 Permanent Magnet, Defect of, 376 ^^ Permanent Magnet, Direot- Beading, 76 Spring Control, 877 Standard, 422 with Magnifying Gearing, 386 Beet Material for Coils of, 420 Best Material for Cotls of Ex. 