Part 137

=Ink=, how does a blotter take up? 18

=Instruments=, artillery, testing, 24 musical, 488 optical, based on refraction, 38

=Incandescent lamp=, development of, 306

=Inside= of a mine planting submarine (illus.), 277

=Iron=, cast, 265 melts at, 35 the most valuable metal, 265 wrought, 265

=Is= a moth attracted by a light? 288 man an animal? 180 the hand quicker than the eye? 376 there a reason for everything? 200 there a man in the moon? 400 yawning infectious? 192

=Jacket=, of a gun, 54

=Japan= the natural home of the silk worm (illus.), 112

=Kentucky rifles=, 45

=Key=, how it works in a lock (illus.), 491

=Knots=, different kinds of (illus.), 363 what makes, in boards, 223

=Lambs=, Siberian, in South Dakota (illus.), 80

=Lamps=, first street light in America, 296 the Clanny safety, 264 did candles come before? 294 earliest forms of, 295 Edison’s first (illus.), 306 incandescent carbon (illus.), 306 incandescent, development of, 306 incandescent, electric, when invented, 305 French watch tower (illus.), 295 Mazda (illus.), 306 from Nushagak hanging (illus.), 297 Pagan votive (illus.), 296 Tantalum (illus.), 306 street, when first used, 295 chimney protects flame, 37 coal miners and safety, 262

=Lamp chimney=, why it makes a better light, 37

=Langley, Dr. Samuel P.=, 1914 flight of aeroplane, 128

=Languages=, why so many, 197

=Lantern=, the first oil (illus.), 297 the “Réverbère” (illus.), 297

=Laugh=, when glad, why we, 92 nerves, 93 when tickled, why we, 93

=Laughter=, reflex action, 93

=Lead=, as used in making paint, 267 in a pencil, 468 why so heavy, 267 as used in pipes for plumbing, 267

=Leather=, how the hides are treated, 539 treatment of hides, 538 unhairing machine (illus.), 540 hide house (illus.), 538 tanning process, 539 rolling room (illus.), 539 tanning sole leather, 539 how upper leather is tanned (illus.), 540 disposing of waste material, 540 wringers, 539 tan yard (illus.), 539

=Legs=, not same length, 91

=Lens=, in the eye, 22

=Leyden jar=, what it is, 332

=Life=, beginning of, 174 beginning of man’s, 174 how plants reproduce, 175

=Light=, attracting moths, 288 glow-worms why they glow? 231 how produced, 230 lightning bugs, made by, 231 where it goes when it goes out, 36 what makes match, 198 in mirror, 22 in negative, 23 rays, 36, 495 broken rays of, 38 rays, heat from, 36 and refraction, 38 speed of, 36, 140 travels faster than anything in the world, 36 surrounding earth, 38 wave changed into heat, 36

=Lighting=, arc, how does it burn, 307 in America, first street (illus.), 296 first oil lantern, 297 electric, when introduced, 305 first street light in Paris, 297 gas tank, (illus.), 298

=Lightning=, why it follows thunder, 140