154 



Sextant, Box. A pocket sextant made in the form of a flat 



tubular box. [2, 3, 5, 6, 9, 10, 13, 15, 16, 17, 20, 21, 24, 25, 



26, 27, 28.] 

 Sextant Chronograph. A small chronograph which can be fitted 



into the handle of a sextant. [8, 13, 15, 16, 28.] 

 Sextant, Double. An improved form of sextant for surveying 



and harbour work. Two angles can be observed and measured 



on the one instrument. [2, 10, 13, 15, 20, 21, 26, 27, 28] 

 Sextant Mirrors. The index and horizon glasses. [2, 3, 10, 13, 



15, 16, 17, 21, 26, 27, 28] 

 Sextant, Paget Angle. A circular dial sextant with a geared 



index for use with the Station Pointer (q.v.). [13, 15 ', 27.] 

 Sextant Shades. Optically worked neutral or coloured glass 



discs of varying diameters, used in sextants. [2, 3, 10, 13, 



15, 16, 17, 21, 26, 27, 28] 

 Sextant Stand. Metal counterpoise stand for sextant. [10, 13, 



15, 17, 21, 26, 27, 28] 

 Sextant, Stellar. A special pattern sextant with large mirror 



and telescope for star observation. [10, 13, 15, 16, 17, 25, 



26, 28] 



Shakespear Hydrogen Purity Meter. See Hydrogen Purity Meter. 

 Sheath Dividers. Pocket dividers (q.v.), with sheath for pro- 

 tection of the points. [5, 13, 15, 16, 17, 20, 21, 24, 26, 27.] 

 Sheppard's Cubing Slide-Rule. See Slide-Rule. [15, 21] 

 Ship's Clock. A lever spring timepiece for use on ships, to show 



on the one dial Greenwich and local time. [13, 15, 16. 17, 



28.] 

 Ship Curves. A set of pearwood curves used by naval architects 



in ship design. [6, 13, 15, 17, 21, 24, 26] 

 Ship's Lamps. [15.] 

 Ship Log. See Log. [15.] 

 Ship's Telescope. See Telescope. [3, 6, 8, 9, 10, 13, 15, 16, 17, 



20, 21, 23, 24, 26, 28.] 

 Shutter, Davis. A diaphragm used above the objective of a 



microscope for reducing the aperture. [2, 3, 21, 22, 26] 

 Shutter, Photographic. An apparatus for giving a photographic 



exposure of definite duration. [8, 20, 26.] 



Shutter Tester. An instrument for testing the speed of photo- 

 graphic shutters. [3.] 



Side Angle Thermometer. See Thermometer. [5, 13, 17.] 

 Side Silver Reflector. An instrument for illuminating opaque 



objects on the stage of a microscope. [2, 3, 22, 26] 

 Sidereal Clock. An instrument for showing astronomical time. 



[17, 18, 25, 26.] 

 Sideroscope. An instrument for detecting minute degrees of 



magnetism by a delicate combination of magnetic needles. 

 Siderostat. AnT^astronomical instrument designed to keep a 



star within^the same portion of the field of a telescope for 



observation. [6, 11, 13, 18.] 



