336 



Index 



Fuel, chief elements in, 315-316. 



Fulcrum of lever, 59-60*. 



Fuse gap, the, 241*, 379*- 



Fuses, short circuits and, 240-245. 



Gas, cooling of, on expanding, 94~95 ', 

 carbon and hydrogen in, 315 ; used 

 for filling electric lamps, 317-318; 

 will not burn until hot enough, 323- 

 324 ; an explosion the sudden release 

 of a confined, 348. 



Gases, diffusion of, 269-271 ; as ele- 

 ments, 293-294. 



Gas heaters, action of, 319, 321*, 



322*. 



Gasoline, evaporation of, 103 ; boiling 

 of, 112; distilled from petroleum, 

 114; elements of, 315; action of, 

 in making automobiles go, 344- 



345- 



Geysers, cause of, no. 

 Glass, a poor conductor of heat, 1 1 8 ; 



used as insulator of electricity, 215. 

 Glowworms, reason for glowing of, 



341-342- 

 Gold, an element, 293, 299; plating 



of, 339- 



Gravitation, defined, 3. 

 Gravity, i ; pull of, opposed to pull 



of adhesion, 42-43. 

 Grease, friction diminished by, 53- 



54 ; combined with lye to form soap, 



357- 

 Great Salt Lake, reason for salt in, 



104-105. 

 Greeks, early knowledge of electricity 



possessed by, 196. 

 Green color of water, reason for, 169 



171*. 



Grounded circuits, 225-229*. 

 Gun, shooting of, caused by explosion, 



345-346. 

 Gunpowder, action of, in shooting of 



a gun, 345-346; how made, 347. 



Hail, explanation of, 286. 



Heat, a result of friction, 53; is the 

 motion of molecules, 90 ; not caused 

 by expansion, 94-95 ; cold is absence 

 of, 95, 120; required to evaporate 



liquids, 102-103 ; conduction of, 

 116-118; carried by air, by con- 

 vection, 118-119; radiation of, 122- 

 128; of incandescent lamp, 125-126; 

 brought to focus by convex lens, 

 149; chemical change caused by, 

 323-325- 



Heaters, hot-water, 120*; electric, 

 230, 232; gas, 319, 321*, 322*. 



Heat waves, cause of, 141. 



Hydrochloric acid, getting hydrogen 

 from, 301-304; testing for silver 

 with, 373. 



Hydrofluoric acid, 351. 



Hydrogen, an element, 294, 299; 

 in water, 295-296; experiments 

 with, 301-304*; one of chief ele- 

 ments in fuel, 315-316; part taken 

 by, in burning, 312-319. 



Ice, slight friction of, 52*; action of 

 molecules in, on freezing and melt- 

 ing, 96-97; reason for floating of, 

 98-99. 



Incandescence, defined, 125. 



Incandescent lamps, 125-126; num- 

 ber of electrons in, 197; working 

 of, 229-232. 



Inertia, 667 1 ; definition of, 70. 



Insulators, of heat, 118; of electricity, 

 213; substances used as, 215. 



Iodine, an element, 299; testing with, 

 for starch, 373~374- 



Iron, a good conductor of heat, 118; 

 an element, 299. 



Irons, electric, 229*, 230, 232. 



Iron salt, formed by lemon juice on 

 steel, 353. 



Iron ships, reason for floating, 24*-26. 



Kerosene, boiling of, 112; distilled 

 from petroleum, 114; carbon and 

 hydrogen in, 315. 



Laughing gas, 309. 



Lava in volcanoes, 1 10. 



Lead, an element, 299. 



Lead pencils, arc light from, 233*- 



234*. 

 Leaning Tower of Pisa, 29*~3O. 



