INDEX. 



447 



Heat', sources of, 209 



influence extends how far into the 

 earth, 211 



of cliemical action, 212 



greatest artiticial, 212 



derived from mechanical action, 213 



latent, 213 



sensible, 213 



of vital action, 214 



of friction, 214 



conductors and non-conductors of, 216 



radiation of, 216 



communication of, 216 



conducting power of bodies, how di- 

 minished, 218 



good radiators of, 222 



how propagated, 223 



velocity of, 223 



how reflected, 224 



rays of, what is meant by, 234 



absorption of,. 225 



expansion by, 223 



how transmitted through different 

 substances, 226 



effects of, 227 



Bolar, compound nature of, 227 



force of expansion of, 229 



expansion of, practical illustrations 

 of, 229 



latent, when rendered sensible, 246 



capacity for, 247 



quantity of, different in all bodies, 247 



specific, 247 

 Helix, construction of, 432 

 Horse power defined, 83 

 Houses, haunted, explanation of, 200 

 Humidity, absolute and relative, 263 

 Hurricane, what is a, 285 

 Hurricanes, where most frequent, 2S5 

 space traversed by, 286 

 velocity of, 286 

 Hydraulics, 148 



Hydraulic engines, cause of theloss of power 

 in, 15S, 159 

 ram, construction of, 161, 163 

 Hydrometer, what is a, 141 



uses of, 141 

 Hydrostatics, 123 



Hydrostatic press, construction of, 126, 127 

 Hydro-extractor, 80 

 Hygrometer, how constructed, 269 



Ice, origin of bubbles in, 233 



heat in, 206 

 Images, when distorted in mirrors, 303 

 Impenetrability, 12 



illustrations of, 13 

 Incidence, angle of, 71 

 Inclined plane described, 105 



advantage gained by, 106 

 Induction, magnetic, 421 

 Inelastic bodies, results of collision of, 69 

 Inertia, what is, 10 



examples of, 17 

 Inkstand, pneumatic, 179 

 Insects, how produce sound, 205 

 Insulation, 374 

 Intensity in electricity, what is, 408 



Iron, galvanized, what is, 415 

 how made hot, 206 

 how rendered magnetic by induction, 



421 

 ships, principle of flotation o^ 140 

 soft, how magnetized, 421 

 why stronger than wood, 29 



Kaleidoscope, construction of, 307 

 Key-note, what is, 201 



Lakes, salt, origin of, 124 

 Lamp-wick, how raises oil, 145 

 Lantern, magic, what is, 361 

 Larynx, description of, 203 

 Laughing, what is, 205 

 Law, physical, definition of a, 10 

 Lens, achromatic, 3-8 

 axis of, 321 

 defined, 319 

 focal distance of, 321 

 Lenses, varieties of, 319 

 Level, spirit, construction of, IBT 



what is a, 53 

 Lever, law of equilibrium of the, 94 

 Levers, arms of, 93 



compound, 96 



disadvantages of, 9T 

 kinds of, 93 

 what are, 93 

 Leydenjar, 382 

 Light, absorption of, 300 

 analysis of, 325 

 chief sources of, 294 

 corpuscular theory of, 293 

 divergence of rays of, 296 

 electric, 410 

 good reflectors of, 301 

 how analyzed, 326 

 how propagated, 295 

 how refracted by the atmosphere, 



314 

 intensity of, how varies, 297 

 interference of, 339 

 moves in straight lines, 295 

 polarized, 341 

 polarization of, 343 

 ray of, what is, 295 

 refraction of, 312 

 same quantity not reflected at all 



angles, 305 

 three principles contained in, 344 

 undulatory theory of, 293 

 velocity of, 298 



how calculated, 299 

 vibrations of, 339 

 waves of, 339 

 what is, 292 



when totally reflected, 316 

 white, coinpositi'in of, 326 

 Lightning, identity of with electricity, 393 

 mechauical effects of, 306 

 rods, how constructed, 394 

 space protected by, 395 

 when dangerous, 395 



