Part 135

=Fuse=, for firearms in early history, 45

=Funditor=, 42

=Gas=, acetylene, 305 definition, 348 first structure to be lighted by, 302 in coal mines, 262 water, 305

=Gas, illuminating=, Baltimore first city to use, 302 carbon in, 302 discovered, when, 302 first American house to use, 302 first practical demonstration of, 302 generator house (illus.), 299 holder (illus.), 298 how it gets into jet, 302 how it is purified, 303 how made, 303 how the meter works, 304 hydrogen in, 302 impurities removed from (illus.), 301 jet, the story in a, 303 made of, 302 meter, description, 304 purifying boxes (illus.), 301 removing tar from, 300 shaving scrubbers (illus.), 300

=Gasoline engine= (illus.), 181, 182

=Gases=, generated at gun muzzle, 27 how expelled in gun ingot, 55 hydrogen, 349 nitrogen, 350 oxygen, 349 tendency to put out fire, 37

=Gas-rings=, in firing motor, 27

=Gatling=, inventor of guns, 310

=Gelatine=, in photography, 23

=Gestures=, talking by, 18

=Ghosts=, what are they? 367

=Glad=, why do we laugh when, 92

=Glass=, why it cracks, 63 how long known, 247

=Glass, plate=, casting (illus.), 249 commercial, 246 plate and window glass compared (illus.), 252

=Glass, plate, making=, annealing, oven, 249 beveling, 247 blanketing, 252 clay mixing (illus.), 248 clay trampling (illus.), 248 clay used, 247 grinding table, 250 materials used in, 247 mercury, 253 nitrate of silver, 253 pots (illus.), 248 pots, drying of, 248 pots, length of usefulness, 248 silvering, 247 skimming the pot (illus.), 249 treading, 247

=Glow-worm=, why does it glow? 231

=Gold=, why is it called precious? 266

=Gong=, why does it stop when it has been sounded, 78

=Good luck=, why a horseshoe brings? 311

=Graphite= in lead pencils, 468

=Gravitation=, what is, 267

=Gravity=, center of, in gun, 61

=Gravity=, force of, 61

=Greek fire=, in early history, 44

=Growing=, why do we stop, 195

=Gun=, action at muzzle, 27 annealing a gun ingot, 57 assembling of, 48-54 arquebus of, 1537, 47 barrels, erosion of, 35 blow-holes, 56 bore searcher, 59 breech of a, 53 discharges, force of, 33 calibre of a, 53 elastic limit, 58 elongation, 58 forging a (illus.), 52 heat treatment, 58 hoops of a, 54 improvements in, 45 ingot, calibre of, 55 jacket of, 54 length of a, 53 liner of, 54 life of, 35 manufacture in America, 48 measuring inside diameter (illus.), 59 modern built-up (illus.), 54 mold for ingot, 55 muzzle of, 53 pressure generated in a big gun, 54 photography (illus.), 33 piping, 56 powder chamber of a, 53 rifling (illus.), 60 rifling of, 53 shrinking pit, 59 tensile strength of, 58 factory, testing materials, (illus.), 50 tube of, 54 tube, how it is tempered, 57 why called gatling, 310 wire-wound, 54

=Gun-barrels=, imported from England, 49 resisting pressure of, 34

=Gun-cotton=, in smokeless powder, 35, 206