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On a wooden base, provided with levelling screws, a graduated copper rule, about a yard long, is fixed edgeways. On this rule the various parts composing the apparatus are placed, and their distances can be fixed by means of binding screws. a is a support for a Locatelli's lamp, or other source of heat; F and E are screens; C is a support for the bodies experimented on, and m is a thermo

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electrical battery. Near the apparatus is a galvanometer, D, which has only a comparatively few turns of a tolerably thick (1 mm.) copper wire. Such galvanometers are called thermomultipliers. The delicacy of this apparatus is so great that the heat of the hand is enough, at a distance of a yard from the pile, to deflect the needle of the galvanometer,

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Blood globules, 8

Binocular vision, 372
Biot's experiment, 396
Baroscope, 149

Bodies, equilibrium of, 44; general
properties of, 6; internal consti-
tution of, 4

Boiling, 232; laws of, 233
Boiler, steam, 256

Bologna, Tower of, 46

Boyle's law, 132

Brahma's press, 82

British units, 103

Buffon's burning mirrors, 201

Bulging of earth at the equator, 30

Bunsen's battery, 447; burner, 338
Bunsen and Kirchhoff's researches,
337, 338

Bunten's barometer, 122
Buoyancy of liquids, 79

Burning glasses, 331; mirrors, 201

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Condensers, limit of charge of, 414
Condensing electroscope, 417; en-
gine, 254; plate, 417; pump, 141

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DAGUERREOTYPE, 366

Damper of piano, 177

Dancing puppets, 406
Daniell's battery, 446; hygrometer,

262

Dark lines of the spectrum, 336
Decomposed force, 25
Decomposition of water, 451
Declination, 381

Degrees, Fahrenheit, 190; Réaumur,

190

Density 2, of gases, 218
Despretz's experiment, 449
Developer, 366

Dew, 273; point, 262

ELE

Dial telegraph, 468
Diamond, 313

Differential thermometer, 193
Diffused light, 298

Digester, 235

Dip, magnetic, 383
Dipping needle, 383

Discharge, slow and instantaneous,

413

Discharger, universal, 421

Discharging rod, 413

Dispersion of light, 333

Dissolving views, 360

Dissonance, 169

Distance of distinct vision, 371

Distillation, 242

Divisibility, 8
Diorama, 368
Drum, 154
Ductility, 71

Dynamometer, 22

Dominant chords, 169

Dove's law of rotation of winds,

279

Double action machine, 249; descrip-

tion of, 250

FAR trumpet, 165

Earth currents, 434

Earth, flattening of at the poles, 30;
radius of, 30
Ebullition, 232
Eccentric, 251
Echoes, 161
Eolipyle, 248

Egg, electric, 408

Elastic force of aqueous vapour, 236;
fluids, 108

Elasticity, 12, 13

Electric batteries, 416; egg, 408;

spark, 405, 421; telegraphs, 468
Electric discharge, effects of, 418;
phenomena of, 418; physiological
effects of, 418

Electric light, 450; stratification of,
482; electric alarum, 476; attraction
and repulsion, 391; chimes, 405;
condensers, 412; discharge, mag-
netic effects of, 425; machine, 399;
measurement of charge of, 400;
pendulum, 388; portraits, 422;
whirl, 407

Electrical fluids, hypothesis of two,
390; positive and negative, 390
Electricity, 386; atmospheric, 427

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Galvanic shock, 448
Galvani's experiment, 436
Galvanometer, 459; uses of, 459
Gases, 5, 108; conductivity of, 209;
density of, 218; expansibility of, 5,
IIO; laws of mixture of, 135;
liquefaction of, 244; permanent,
244; value of the expansion of, 216;
weight of, III

Gases and liquids, mixture of, 136
Gauss and Weber's electro-magnetic
telegraph, 468
Ghost scenes, 369
Glasses, weather, 127
Globe, luminous, 410
Globules, 8

Glaisher's factors, 262

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