362 



OUR PHYSICAL WORLD 



Horn, French, 325 



Hornblende, 50, 58, 65; characteristics 



of, 58, 61 



Horse-power, 183, 191, 228 

 Hot- water heating, 154 

 House, wiring of, 247, 248 

 Humidity, 155 



Humor: aqueous, 305; vitreous, 305 

 Hyades, 31 

 Hydra, 42 

 Hydrochinone, 317 

 Hydro-electric plants, 125, 126 

 Hydrogen: atom of, 165; discovery of, 



1 06; molecule of, 163, 165 

 Hygrometer, 155 

 "Hypo," 318, 319 

 Hyposulphite of soda, 318, 319 



Iceland spar, 55 



Illinois, bed rock of, 71 



Illumination: intensity of, 282; meas- 

 uring, 282 



Image: in curved mirrors, 289, 290; 

 in plane mirror, 286, 287; with a lens, 

 296 



Images, multiple, 289 



Inca, 12 



Incandescent lamp, invention of, 246 



Inclined plane, 348 



Inductance, 255, 258, 260 



Induction, 210, 242 



Induction coil, 195, 252 



Inertia, 83, 132. 



Injector, 186 



Intensifying, directions for, 324 



Interrupter, 245 



Iodine, in, 172 



Iron, 45, 159; burning of, 176; pig, 

 1 60 



Iron furnace, 159 



Iron, oxide, 176 



Iris of eye, 303 



Isis, ii 



Joule, 228 



Juno, 21 



Jupiter, 2, 7,9, 11, 13,39 



Kaleidoscope, 289 



Kaolin, 50, 58, 59, 60; characteristics 

 of, 59, 60 



Kettle drum, 325 



Kids, the, 30 



Kilns, charcoal, 159 



Kilowatt-hour, 228, 229 



Kite, 78; bird, directions for making, 

 82; bow, 84; box, 79, 84; bridle for, 

 81; invention of, 78; Franklin's, 

 204; tail of, 83; tetrahedral, 83, 84 



Kites: explanation of flight, 79; flying, 

 78, 79, 84; games with, 84; map- 

 ping with, 79; weather observations 

 with, 78 



Knife, 349 



Krypton, 167, 170 



Kyak, 120 



Labradorite, 57 



Langley, S. P., 92, 93 



Lantern slides, directions for making, 323 



Larynx, 336 



Latham, Herbert, 95 



Lavoisier, 150 



Law of: Ampere, 207; Archimedes, 

 115; definite proportions, 168; elec- 

 tric pressure, 226; fluid pressure, 114; 

 induced electric current, 210; inten- 

 sity of illumination, 282; lever, 341, 

 342; light propagation, 281; light 

 reflection, 286; light refraction, 293, 

 294; machines, 340; Mendeleeff 

 (periodic), 168, 170; Oersted, 207; 

 pulleys, 347; screw, 349; vibrating air 

 columns, 331; vibrating strings, 329 



Laws of nature, 281 



Lead, 173 



Leda, 35 



Legends, Greek, 18, 19, 21, 27, 29, 31, 32, 

 33,34 



Lemon squeezer, 343 



Lens, 292, 295, 296; crystalline, 288, 

 305; focal length of, 257; focus of, 

 295; image formed by, 296; uni- 

 versal, 309 



Lenses: grinding, 303; making, 298; 

 shapes of, 297 



Leo, 36, 37 



Levers, 339-42; kinds of, 343; law of, 

 34i, 342 



