Pressure gauges, 143 Priestly, investigations of, 73 Primary colours, 213 Prisms, reflection of, 85 Process blocks, 186 Projectiles, velocity of, 237 Propellers of the torpedo, 99 Propellers, testing aerial, 203 Prout's anonymous essay, 74 Prussiate of potash, 177 Purification of metals, 62 Q Quadrant electrometer, the, 35 Quartz, 113; fibre, 31, 131 R Radium, 33 Ramsey, Sir W., 75 Range-finding, 240, 242 Rayleigh, Lord, 74 Receiving instruments for wireless, 162 "Record" vanner, the, 116 "Rectifier," the, 37, 171 Red rays of light, 82 Reflection by prisms, 84 Reflectors, lighthouse, 84 Reiss electrical thermometer, 36 Repeated-impact testing machine, 204 Rescue teams for colliery accidents, 221, 222 Resistance welding, 126 "Resonance," an experiment, 160 Reviving apparatus for coal mines, 229 Rheostat, the, 188, 191 Rhigolene, 45 Rifling of a gun, 239 Rubber, synthetic, 44 Rubies, artificial, 131 Rudders of a torpedo, 100 Rutherford, Prof., 33, 168 S Saccharine, 48 Saltpetre, 12 Schwartzkopff torpedo, the, 99 Scilly Island lighthouse, 80 Sea, gold in the, 120 Secondary battery, the, 62 "Sectors," 81 Selenium, 184 "Self-rescue" apparatus, a, 228 Shale, oil from, 45 Shells for guns, 239 Ships, testing by models, 200 Short circuit, 179 "Shunt," the, 165 Sighting a big gun, 241 Silica, 133 Skating rinks, ice in, 71 "Sludge" and "effluent" of drainage, 233 Spark detectors, 166 Spark-gap, 162 Spectrum, the, 213 Spinthariscopes, 33 Spirits, 52 Springs, testing, 203 Stamps for crushing quartz, 113 Starch grains in colour photography, 217 "Step-down" and "step-up" transformers, 127 "String galvanometer," the, 30 Submarine mines, 104 Submarine telephone, 88 Sulphuric acid, 11, 43 Sunlight, composition of, 213 Synchronism, difficulties of, 182, 191 Synthetic substances, 44 T "Tamping," 15 Tank for testing at Teddington, 201; New York harbour, 201 Telautograph, the, 180 Telectograph, the, 180, 185 Telegraph key for wireless, 162 Telewriter, the, 187 Temperature, measuring, 38 Tesla, Nicola, 164 Testing by heat, 205 Testing machines, 206 Thermit, 135 Thermo-couple, the, 38 Thermo-galvanometer, the, 37 Thomson Mirror Galvanometer, the, 28 Thomson, Prof., S., 159 Torpedo, the, 98 Training station at Porth, 225 Transformer, the, 127 Transmitting instruments, 163 Travers, Prof., 75 Tree stumps, blasting, 19 Tuning-fork a standard of speed, 193 Turret of a battleship, 240 U Ultra-microscope, the, 209 Ultra-violet rays, 172 V Varley and the Atlantic cable, 28 Vaseline, 46 Veins or lodes, 113 Vickers, 202 Voltmeter, the, 26 Volts, 22, 24 W Water a source of heat, 124 Water, soft and hard, 232 Watt, the, 24