Candles to measure time, 46 Chaldean day, 15 Chaucer, 56 Chronographs, 179 Chronometer, 165 Chronometer escapement, 166 Clock movement, 123 Copernicus, 56 Crossbow experiment, 183 Crown wheel, 115 Cycloid, the, 109 Dante’s Inferno, 54 Day, length of, 29 Dead beat escapement, 135 Density, 12 Driving weight, 127, 141 Earth, a sphere, 21 Earth’s motion, 57, 69 Earth not at rest, 67 Egg-boiler, 43 Electric clocks, 179 Epicycloidal wheels, 191 Escapements, anchor, 120 crown, 115 chronometer, 166 dead beat, 135 gravity, 169 Falling bodies, laws of, 62 Force, 76 Forces, revolution of, 89 Fusee, the, 117 Galileo’s “Dialogues,” 58 clock, 111 Grandfather’s clock, 119 Gravity, action of, 13, 65 Gravity escapement, 169 Greek day, 16 Harmonic motion, 97 Hooke’s law, 71 Isochronism of springs, 93 Lamps to measure time, 46 Latitude and longitude, 161 finding, 163 Mass, nature of, 10 Mercury clock, 45 Modern methods, 177, 197 Moments, 101 Moon’s appearance, 17 Motion, reliability of, 57 Musical notes, 95 North pole, days at, 33 Oscillations, law of, 151 Parabola, the, 87 Pendulum, the, 103, 145 suspension, 145 mercury, 147 gridiron, 149 theory of, 155 free, 133 Pisa, leaning tower of, 61 Planets, names of, 11 Pulse measurer, 99 Ratchet wheels, 129 Roman clocks, 40 Sand-glasses, 41 Space, nature of, 8 Speed of falling bodies, 79 Spring balance, 107 Stevinus’ theory, 81 Style of sun-dials, 35 Sun-dials, 27 to make, 48 Synchronous clocks, 175 Time, 13 Toothed wheels, 125, 137 Tuning fork, 94, 181 Velocities, composition of, 85 Water pressure, 37 Water clocks, 39 Watches, 156 Week days, names of, 24 Wheels, shape of teeth, 190 Wheel-cutting machines, 193 Winding drum, 131 Winter sun, 31 Zodiac, 18 BRADBURY, AGNEW, & CO. LD., PRINTERS, LONDON AND TONBRIDGE. * * * * * * Transcriber’s note: Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in this book; otherwise they were not changed. Simple typographical errors were corrected; occasional unpaired quotation marks were retained. Ambiguous hyphens at the ends of lines were retained. Square roots are represented as √(values). Index not checked for proper alphabetization or correct page references. Page 16: “six o’clock” was printed as “six clock”; changed here.