Index 



387 



Lemon juice, action of, on silver and 

 on steel, 353 ; litmus test of, 359. 



Lens, of eye, 142, i5i*-iS3 ; of camera, 



* 143, 149*, 328; convex, 148-149; 

 concave, 149*; in telescope, 157. 



Levers, 57-65*. 



Light, radiation of, 122, 123*-! 28; 

 reflection of, 129-135*; refraction 

 of, i36*-i4i; focus of, 142-149*; 

 brought to focus by convex lens, 

 149; diffusion of, 158-161*; color 

 a kind of, 162 ; speed of, 182 ; chem- 

 ical change caused by, 326-335; 

 and manufacture of food in plants, 

 332-333- 



Lightning, cause of, 200-201. 



Limewater test for carbon dioxid, 

 375*~376. 



Liquid air, 97, 112. 



Liquids, absorption of, 36-40; dif- 

 fusion in, 272. 



Litmus paper, experiments with, 358- 

 359- 



Litmus test, the, 358-359. 



Lye, a common base, 356; experiment 

 with, 356; soap made from, 357; 

 used for clearing out drainpipe, 

 358; neutralization of, by acids, 

 363- 



Machinery, oiling of, to decrease 



friction, 53-54. 



Magdeburg hemispheres, 15, i6*-i7- 

 Magnetism, 190 ff. 

 Magneto, of automobile, 210, 211*; of 



old-fashioned telephone, 210-211. 

 Magnets, 190-195*. 

 Magnification, 150-157; by concave 



mirror, 157. 

 Magnifying glass, convex lens in, 149 ; 



operation of, 150-156*. 

 Manganese dioxid, an essential in 



explosives, 347. 

 Megaphone, working of, 184. 

 Melting, freezing and, 96-99. 

 Membrane, diffusion through a, 272. 

 Mercury, cohesion of, 47-48*; use of, 



in thermometer, 89*, 90-91 ; an 



element, 299. 

 Mercury-vapor lamps, 167-168*, 172. 



Metals, good conductors of heat, 118; 

 good conductors of electricity, 215; 

 as elements, 310; plating of, 336- 

 339*; action of acids on, 351-353- 



Microscope, 88; working of, 155- 



157*. 



Mirrors, concave, 154*, 155*, 157. 



Mixtures, distinguished from com- 

 pounds, 300-310. 



Molecular attraction, 36 ff. 



Molecules, pull of, on each other, 46- 

 47 ; explanation of, 88-89 > heat 

 defined as the motion of, 90 ; action 

 of, in evaporation, 102-103* ', action 

 of, in boiling water, 107 ; action of, 

 in conduction of heat, 117; action 

 of, in radiation of heat and light, 

 125; action of, in magnetizing, 

 194* 195; made up of atoms, 196, 

 310; mingling of, 259 ff. ; action of, 

 in formation of clouds, rain, and 

 dew, 277. 



Moon, cause of ring around, 131. 



Morse telegraph code, 253. 



Motion-picture machines, lenses of, 

 143, 148. 



Motor, the electric, 255-257*. 



Mountains, rainfall on, 286-287. 



Musical instruments, pitch of, 185- 

 187*, 1 88; vibrating devices of, 188. 



Nail plug, the, 241*, 379*. 



Needle, magnetizing of, 192*, 193*- 



195- 

 Negative charges of electricity, 198- 



200. 

 Neutralization of acids and bases, 360- 



364- 



Niagara Falls, electricity generated 

 by, 210. , 



Nickel, an element, 299. 



Nickel-plating copper, process of, 336- 

 339*. 



Night, reason for coolness at, 127-128. 



Nitric acid, etching copper with, 352*- 

 353 ; action of, on cloth, 354*. 



Nitrogen, an element, 299; a non- 

 burning gas, 308; used in electric 

 lamps, 317. 



Northern Lights, cause of, 193. 



