Gives two beats on the transmission of 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; circuit, general arrangement, _152_, 153; exchange, _154_, 155. Telephony, submarine, 157. Telescope, 257; Galilean, _259_; prismatic, _260_; reflecting, 260; terrestrial, _259_. Threshing-machine, 447, _448_. Thurston, Professor, 31. Tides.