167 



Telestereoscope. An instrument for producing an appearance of 

 relief in the objects of a landscape at moderate distances. 



Telethennometer. An apparatus for determining the temperature 

 of a distant point, as by a thermo-electric current or other- 

 wise. See also Pyrometer, Thermometer. [4, 13, 16.] 



Telewriter. A telegraphic apparatus for reproducing writing at 

 a distance. 



Tellurian. A working model for showing the revolution of the 

 earth round the sun. 



Temperature Control Apparatus. For maintaining constant tem- 

 perature baths for standard cells and coils. See also Thermo- 

 stat. [4.} 



Templets. Arcs of large radii cut in wood, used as a guiding 

 edge in drawing arcs. [21.] 



Tennant's Nitrometer. See Nitrometer. 



Tension Meter. An instrument for measuring the tautness of 

 aeroplane fabrics. 



Terrascope. Model of the earth and sun. [15.] 



Terrestrial Globe. A sphere representing the earth, and having 

 the seas, continents, and islands, etc., indicated thereon. 

 [15, 21.] 



Test-Gauge, Duplex Standard. A double reading standard gauge 

 used in the testing of gauges. [5, 13, 15, 17, 28.] 



Test Plate (Abbe). A silvered glass plate with rough edged lines 

 ruled upon it. Used for testing microscope object-glasses. 

 [2, 3.] 



Test Types. Printed type on card for eyesight testing. [2, 26.] 



Tetanometer. An electrically controlled apparatus used in 

 physiological experiments for stimulating a nerve by rapid 

 concussion. 



Tetragonal Prism. The same as Corner Cube Prism (q.v.). 



Thacker's Calculating Instrument. See Calculating Instrument. 

 [13, 27.] 



Thacker's Slide-Rule. A surveying instrument. [13, 21, 27.] 



Thaumatrope. An optical toy depending for its effects upon the 

 persistence of vision. 



Theodolite. A surveying instrument for accurately measuring 

 both horizontal and vertical angles by the aid of a telescope 

 and graduated circles. It is usually mounted on a strong 

 tripod and is provided with compass, level, etc., and verniers 

 for reading the circular scales. See also Dunbar-Scott 

 Auxiliary Top and Side Telescope. [2, 5, 6, 9, 10, 13, 15, 

 16, 17, 20, 21, 24, 25, 26, 27.] 



Theodolite, Lean's Miners'. A special form of theodolite for 

 mining work. [6, 13, 18, 21, 25.] 



Theodolite, Transit. A theodolite in which the telescope may 

 take a complete revolution upon its horizontal axis. In the 

 " plain " theodolite the telescope moves through an arc of 

 about 45 upwards or downwards from the horizontal plane. 

 [2, 5, 13, 15, 16, 17. 20, 21, 24, 25, 26, 27.] 



