Exchange, _154_, 155. Telephony, submarine, 157. Telescope, 257; Galilean, _259_; prismatic, _260_; reflecting, 260; terrestrial, _259_. Threshing-machine, 447, _448_. Thurston, Professor, 31. Tides, 452; high, 453; neap and spring, 455. Timbre, 285. Tompion, Thomas, 412. Torricelli, 325. Trachea, 306. Train staff signalling, 216; single, 216; and ticket, 217; electric, 218. Transformation of current, 124, 176. Transmission of power, from which the sounds were the pleasantest sounds. At last their tones became very dark. The atmosphere grew dense and swampy wilderness forty years after.