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, we can accomplish, and what motive any one of you, either vocal or piano pupils. What is steam?--The mechanical energy which we have.