Part 139

=Mine cars= (illus.), 260

=Mines=, clearing channel of buoyant, 283 exploding submarine, 34 planting submarine, inside of (illus.), 277 workers that never see daylight, 258

=Mirror=, collects rays of light, 22 reflection in, 22 reflects rays of light, 22

=Mirrors=, beveling (illus.), 251 how made, 251 how silvered, 252 polishing, 251 roughing, 251 silvered with mercury, 253 silvering mirror plates (illus.), 252

=Molecule=, how big is a, 348 what is a, 348

=Monasteries=, where gunpowder was manufactured, 44

=Money=, how originated, 455 metallic forms of, 456 who made the first cent, 458 who originated, 455 why do we need, 455 why gold and silver are best for coining, 457

=Monitor and Merrimac=, fight of, 32

=Monks=, making gunpowder, 44

=Monoplane=, flying boat (illus.), 135 German (illus.), 132 over Mediterranean (illus.), 132

=Moon=, why it travels with us, 399 the man in the, 400

=Morse, S. B.=, inventor of telegraph, 420

=Mortars= (illus.), 26

=Mothers and Fathers=, do plants have, 175

=Moths=, attracted by light, 288 emerging from cocoon (illus.), 117

=Motion= bodies, swiftest, 25

=Motion=, is train harder to stop than start? 223 of light, 140 of sound, 140 perpetual, 61 perpetual, in mechanics, 240

=Motors=, gas, used in aeroplanes, 130

=Mountains=, what made them, 401

=Moving pictures=, Board of Censors, 373 developing room (illus.), 372 drying room (illus.), 373 continuous movement of film, 376 exact size of film, 370 first camera, 375 first exhibited at studio, 372 how made, 369 how freak pictures are made, 376 negative, stock, 370 negative, perforated, 370 “Pigs is Pigs” (illus.), 374 rehearsing (illus.), 371 scenario (illus.), 374 staging, 371 taking a (illus.), 373

=Mulberry trees=, food for silk worms (illus.), 112

=Mules and drivers= (illus.), 258

=Multiple switchboard= of telephone, 69

=Music=, harp, 479 lyre, 479 note, what it is, 490 what pitch is, 489 what is, 478

=Musical talking machines=, 490

=Muzzle=, of a big gun, 53

=Muzzle-loaders=, in Civil War, 47

=Nails=, why they get hot when hammered, 230