Telephone, Chs. XV, XVI, 134, 145. author's first experiment, 91. experiments, 123. caveat, 135. speech receivers, 139. boys' telephone, 141. first specification of, on record, 143. how telephone talks, 145. simple construction, 146. two methods of transmission: magneto and varied resistance, 142, 149. limit of transmission, 153. central station, 164. affected by heat-lightning, 183. Telephote, 173. Thales of Miletus first described electrical properties of amber, 6. Theophrastus mentions amber, 6. Thermo-electric pile, 75. Torpedo, the, 6. Transformers at Niagara, 200. Transmission, multiple, Ch. XIII, 114. Trowbridge, Prof., telephones through the earth, 188. Tunnel at Niagara, 190. Tyndall, and Gray's experiments, 92. Unrest of the universe, 38. Volt, unit of electrical pressure, 85. Volta, Alessandro, and the voltaic pile, 13. Watt, James, 86. unit of electrical power, 86. Way duplex system, Ch. XIV, 129. Wheatstone transmits musical tones mechanically, 92. needle telegraph, 108. dial-telegraph, 159. Wireless telegraphy, Ch. XXI, 176. signaling by ether-waves, 176. Morse and Henry, 177. Trowbridge, Dolbear, Hertz, 178. Branly, Marconi, 179. Marconi's system, 180. by earth-currents, 182. Wolimer, King of Goths, a natural battery, 7. End of Project Gutenberg's Electricity and Magnetism, by Elisha Gray