Atmosphere, pressure of, 154, 168 Atmosphere, how it moves with the earth, 188 Atomic theory, 15 Attraction, nature of, 53 Attraction, capillary, 72 Attraction between masses, 73 Attraction between solids and liquids, 69 Attraction, Newton's idea of, 54 Attraction, universality of, 77 Attraction, variety in results of, 87 Attraction, opposition between modes of, 88 Attraction, proportion of the mutual motions of, 76 Balloons, 149, 280 Balloon, hydrostatic, 159 Barometer, 169 Barker's mill, 182 Battery, electrical, 387 Berkeley, his ideas of matter, 2 Boats, why they float, 139 Boiling point as affected by the pressure of the air, 171 Brittleness, 29 Buds in winter, 308 Bulk, relation of, to resistance of liquids and gases, 193 Camera obscura, 352 Canals, 117 Capillary attraction, 72, 86 Cartesian image, 159 Centre of gravity defined, 96 Centre of gravity, support of, in animals, 106 Centre of gravity, movements of, in walking, 107 Centre of gravity in relation to attitudes, 108 Centre of gravity in floating bodies, 145 Centrifugal force, 213 Centripetal force, 213 Chimneys, draught of, 282 Clothing, object of, 306 Clouds, how formed, 288 Clouds, colors of, 364 Clouds, shapes of, 289 Clouds, latent heat in, 324 Cocoons, constructed for winter, 307 Colors of objects, 363 Colors of the clouds, 364 Cohesion, strength of, 68 Cohesion, what is essential to it, 66 Cold, absence of heat, 270 Cold at great heights, cause of, 322 Cold from evaporation, 326 Compressibility of substances, 35 Compressibility of air, 152 Condenser, 162 Conductors of heat, 298 Conductors of electricity, 375 Conduction of heat, 297 Conduction, relation of density to, 300 Conduction in liquids, 301 Conduction, influence of, on sensation, 310 Convection of heat, 296 Coverings of animals suited to climate, 305 Crystallization, 62 Daguerreotype, 369 Dams, 122 Davy's safety-lamp, 299 Dawn explained, 346 Density, 24 Dew, formation of, 315 Dew-drops, colors in, 367 Dew-point, 317 Diatonic scale, 267 Draught of chimneys, 282 Drowning, how it can often be prevented, 141 Earth, globular form of, 61 Earth, roundness of, shown, 113 Earth, attraction toward centre of, 80 Earth, thickness of its air-covering, 150 Earth, shape of, influenced by centrifugal force, 218 Earth, rotation of, affecting winds, 284 Elasticity, 39 Elasticity, definition of, 42 Electricity, origin of the term, 370 Electricity, attraction and repulsion in, 371 Electricity, vitreous and resinous, 372 Electricity, galvanic, 394 Electricity, universality of, 378 Electricity, discharge of, from points, 383 Electricity, sound of, 389 Electricity, heat produced by, 391 Electricity, mechanical injuries by, 390 Electrics and non-electrics, 377