Cobalt-Hygrometer. A hygrometer made by dipping unsized 

 paper into a solution of cobaltous chloride, sodium chloride, 

 and a little gum arabic. It is slightly hygroscopic. [13.] 



Cobweb Micrometer. See Micrometer. [2, 3, 17, 21, 22, 26, 27.] 



Coddington Lens. See Lens. [2, 3, 8, 9, 13, 15, 17, 20, 21, 22, 

 24, 26, 27.] 



Coddington Magnifier. See Magnifying Glass. [2, 3, 5, 9, 13, 

 15, 17, 20, 21, 22, 24, 25, 26, 27.] 



Ccelostat. A mirror made to move automatically to direct a 

 beam of light from a star in a constant direction. [11, 14.] 



Coffin Averaging Planimeter. See Planimeter. [10, 13, 15, 16, 

 21, 24, 28.] 



Coleman Archbutt's Viscometer. See Viscometer. [13.] 



Colliascope. A model for teaching the practice of the rule of 

 the road at sea. [13, 15.] 



Colliery Barometer. A mercurial barometer with a special scale 

 for use in coal mines. See Barometer. [5, 6, 13, 16, 17, 

 21, 24, 27.] 



Collimator. A telescope arranged to transmit a parallel beam 

 of light and used to determine errors of collimation. [1, 2, 

 3, 8, 9, 13, 17, 18, 20, 21, 22, 24, 25, 26, 27.] 



Collimator, Floating. A form of artificial horizon. 



Colliograph. A complete set of small models of the various types 

 of vessels and craft, together with a plan board and scale 

 and other details, as used in the Admiralty Court. [15.] 



Colorimeter. An instrument for measuring depth of colour, 

 especially of a liquid, by comparison with a standard. See 

 also Tintometer. [17, 21.] 



Colorimeter, Stammer's. A colorimeter for use with mineral oils. 



Colorimeter, Stokes's. See Colorimeter. [21.] 



Colorimeter, Walpole's. An instrument for the titration of 

 coloured fluids. 



Colour Perception Apparatus. An instrument for testing the 

 colour perception of the eye. [9.] 



Colour Perception Lamp. A special form of lamp devised by Dr. 

 Edridge Green for the detection of colour-blindness. [2.] 



Colour Screen. See Filter. 



Colour Test (Edridge-Green). A test for the detection of colour- 

 blindness. [2, 9.] 



Combustion Recorder. An apparatus for analysing boiler-flue 

 gas and recording the percentage on a chart. [8, 17.] 



Comet-Finder. A telescope of low power, having a large field 

 of view, used for finding comets. [2, 3, 11, 17, 27.] 



Communicator. (i) An instrumental device for transmitting to 

 a secondary dial or register the reading of a primary instru- 

 ment. It may be electrical or mechanical. (2) An electrical 

 or mechanical device for communicating orders on an 

 aeroplane, motor-car, etc. 



