174 



Time-Marker. An instrument for recording to the tenth of a 

 second the time of fall of a body through a known distance. 



M 

 Tintometer. An optical colour-testing instrument, used by 



dyers and printers. See also Colorimeter. [2, 17, 21, 26.} 

 Tintometer, Lovibond's. An instrument for denoting tints and 



colours by reference to standard coloured glasses, used for 



ascertaining the strengths of solutions by means of their 



colours. [3, 5, 13, 17, 21, 26.] 

 Tithonometer. An instrument for noting the tithonic or 



chemical effect of the rays of light. 



Titrating Apparatus. An apparatus used in plant physiology. 

 Tonometer. (i) An instrument for determining the rate of 



vibrations in tones. (2) An apparatus for studying and 



registering the action of various fluids and drugs on the 



excised heart of various animals. (3) An instrument for 



measuring tension, especially that of the eyeball. 

 Tonophant. A modification of the kaleidophone (q.v.) for 



showing composition of acoustic vibrations. 

 Topophone. An instrument to determine the direction of a 



source of sound. 

 Totalising Rain-Gauge. See Rain-Gauge. [13, 15, 17, 20, 21, 



25, 27.] 

 Tourmaline. A mineral occurring usually in three-sided or 



six-sided prisms terminated by rhombohedral or scaleno- 



hedral planes. [2, 26.] 

 Tourmaline Analyser or Polariser. A crystal used for polarising 



light. See also Polariser. [3, 26.] 

 Tracer. A drawing instrument used for copying purposes. [-75, 



24, 27.] 

 Tracheotomy Tube. A tube placed in an opening in the trachea 



to permit passage of air to the lungs in the case of obstruction 



of the larynx. 

 Trajectograph. A simplified form of ripograph, for recording 



altitude and velocity. [13, 20] 

 Trammel. An ellipsograph consisting of a cross with two 



grooves which iorm guides for two pins on a beam compass. 



[2, 17, 21.] 

 Transit. An instrument resembling a large theodolite used by 



surveyors and engineers, and especially for ascertaining 



correct time of passage of heavenly bodies over the meridian. 



[2, 10, 11, 13, 15, 17, 21, 24, 25, 26, 27] 

 Transit Circle. A transit instrument with a graduated circle 



attached, used for observing the time of transit and declina- 

 tion at one observation. [11, 13, 17, 21, 25, 26, 27] 

 Transit Instrument. A telescope mounted at right angles to a 



horizontal axis, on which it revolves with its line of collima- 



tion in the plane of the meridian ; used in connection with 



