Aeroplane, 184.
Air-pressure, 23.
Air-pump, 20.
Air-ships, 173.
Air thermometer, 13.
Alternating current, wonders of, 225.
Amber, 8.
AmpÈre, 67, 111.
Arago, 69.
Archimedes, 1, 12;
inventions of, 7.
Archimedes' principle, 6, 12.
Arc light, 120.
Armature, 101, 103, 104.
Balloons, 174.
Barometer, mercury, 19, 25;
water, 23.
Battle of Syracuse, 2.
Bell, Alexander Graham, 141.
Blake transmitter, 146.
BlÉriot, 190.
Boyle, 23.
Branly, 214.
Cannon experiment, Rumford's, 59.
Cog-wheels, first used, 8.
Coherer, 214.
Colors in sunlight, 31.
Condenser in steam-engine, 40.
Conductors, electrical, 44.
Controller, 116.
Daniell cell, 89, 127.
Davy, 56, 61, 96.
De Forest, 224.
Diamonds, manufacturing, 206.
Drum armature, 104.
Dry battery, 91.
DuFay, 45.
Dumont, 179.
Duplex telegraphy, 136.
Dynamo, 55, 79, 81, 96, 99, 100, 105, 111;
series wound, 105;
shunt wound, 107;
compound wound, 108.
Edison, 95, 105, 114, 121.
Electrical machine, 23, 44, 45, 83.
Electric battery, 53, 62, 84, 89.
Electric charge, two kinds, 45.
Electric current, 50, 69, 73, 74, 82, 96;
magnetic action of, 66, 68;
produced by a magnet, 72.
Electric furnace, 205.
Electricity, 8, 50;
theories of, 49;
speed of, 133.
Electric lighting, 97, 118.
Electric motor, 71, 97, 111.
Electric power, 111.
Electric railway, 112.
Electric waves, 212.
Electromagnet, 100, 126, 143.
Electromagnetism, 65.
Faraday, 55, 63, 100, 111;
electrical discoveries, 64.
Force-pump, 8.
Franklin, 43, 45, 46, 65.
Galileo, 9, 63;
experiment with falling shot, 12.
Galvani, 50.
Galvanometer, 74, 75.
Gas-engines, 150.
Glider, 186.
Governor, fly-ball, 42.
Gramme-ring armature, 103.
Gravitation, 30.
Gravity cell, 91.
Gray, Stephen, 44.
Guericke, 20, 35.
Gyroscope, 200.
Heat, 59.
Henry, Joseph, 97, 127.
Hero, 8, 164;
engine, 164.
Hiero, King of Syracuse, 1, 6.
Horse-power, 40.
Hydraulic press, 26.
Incandescent light, 121.
Indicator, 41.
Induction-coil, 76, 82, 99.
Induction, electrical, 74.
Insulators, 44.
Inventions of the ancient Greeks 7;
of the nineteenth century, 88.
Kite experiment, Franklin's, 46.
Kites, 27.
Leyden jar, 43.
Lightning-rod, 48.
Lines of force, 99.
Liquid air, 203.
Locomotive, electric, 114;
steam, 155.
Magdeburg, 21.
Magnetic field, 80, 99.
Magnets, 8, 130.
Marconi, 215.
Mayer, Robert, 61, 85.
Mercury vapor light, 125.
Microscope, 18.
Miner's safety lamp, 61.
Monorail car, 201.
Morse, 128.
Napoleon, 62.
Newcomen, 34, 36.
Newcomen's engine, 36.
Newton, 27.
Niagara, 227.
Oersted, 65, 71, 111, 126.
Papin, 35.
Papin's engine, 35.
Pascal, 25.
Pendulum clock, 10, 12.
Perpetual motion impossible, 87.
Phonograph, 147.
Principle of Work, 19.
Prism, 31.
Pump, 8, 19.
Radium, 232.
Reis, Philip, 141.
Relay, 130.
Roentgen, 232.
Royal institution, 56, 61.
Rumford, 57, 59.
Rumford's cannon experiment, 59.
Safety-lamp, 62.
Screw propeller, 171.
Siemens, 100.
Spinning tops, 199.
Steam-engine, 8, 25, 34.
Steam locomotive, 155.
Steam pressure, 23.
Stephenson, 156.
Storage battery, 93.
Sturgeon, 97, 127.
Submarines, 190.
Suction-pump, 8.
Symmer, Robert, 49.
Telegraph, 96, 126;
wireless, 208.
Telephone, 140;
wireless, 221.
Telescope, invention of, 15;
Newton's, 32.
Tesla, 231.
Thermometer, air, 13.
Torpedo, 192.
Torricelli, 19, 35.
Transformer, 80, 82, 99, 227.
Turbine, 163.
University of Padua, 13.
University of Pisa, 10, 12.

Valve-gear, 37, 162.
Volta, 53, 63, 89.
Voltaic battery, 53, 89.
Water-clock, 8, 29.
Water-wheel, 165.
Watt, James, 34.
Watt's engine, 38.
Wireless telegraph, 208.
Wright aeroplane, 188.
X-rays, 232.
Zeppelin, 180.

THE END