Filtration beds, 372. Flute, 308. Flying-machines, 348. Fly-wheel, use of, 244. Sun-dial of Ahaz, 410. Syntonic transmission of wireless messages, 143. Talking-machines, 310. Tapper in wireless telegraphy receiver, 141. Tappet arm, 205. Telegraph, electric, 127; insulator, _133_; needle, _128_; recording, 133; sounder, 132. Telegraphy, high-speed, 135; wireless, 137. Telephone, 147; Bell, _148_; circuit, double-line, 155.