179 



Wattmeter, Recording. A wattmeter giving a continuous and 

 visible record of the work-rate of an electric current. 



Wealemefna. A form of space runner ; a convenient instrument 

 for measuring distances on maps in prospecting. See also 

 Rotameter. [13, 15, 17, 21, 24, 26, 28.] 



Weather-Glass. A barometer (q.v.). [5, 6, 13, 15, 16. 17, 20.] 



Weldon Range-Finder. See Range-Finder. [13, 15, 17, 21, 27.] 



Weston Normal Cell. A type of cadmium cell used as a standard 

 of electromotive force. [4, 16, 19.] 



Wheatstone Bridge. A network, arranged in a particular way, 

 of six electrical conductors. Used, together with a galvano- 

 meter and battery, in electrical measurements of E.M.F., 

 resistance, etc. 



Wheatstone's Photometer. See Photometer. 



Wheel ol Life. See Zoetrope. 



Whipple Temperature Indicator. Used with resistance thermo- 

 meters. The instrument is a form of Wheatstone bridge 

 (q.v.) calibrated to give readings in degrees of temperature. 



[4.] 

 White Cloud Illuminator. A plaster of Paris reflector to put 



over a mirror of a microscope to give a diffused reflected 



light. [3, 26.} 



Whitley Slide-Rule. See Slide-Rule. [13, 15.] 

 Wide-Angle Lens. See Lens. 

 Wilson-Kaye Electrometer. See Electrometer. [4.] 

 Wilson's Chromometer. See Chromometer. 

 Wilson's Double Sliding-Rule. See Slide-Rule. [8, 13, 15.] 

 Wind-Corrector, Notcutt. A celluloid instrument giving range 



and line corrections at sight for a 10 ft. per second wind. 



[15.] 

 Wind-Dial. A dial to show the direction of the wind. [6, 13, 



15. 17.] 

 Wind-Gauge. An instrument for measuring the velocity and 



force of the wind ; an anemometer (q.v.). [6, 13, 15, 16, 17, 



20, 21, 24, 25, 26.] 

 Wire Extension and Rupture Apparatus. For measuring the 



extension of wires to the point of rupture. See also Extenso- 



meter. [19.] 



Wollaston's Double-Image Prism. See Prism. [3, 13, 14, 22, 26.] 

 Wright's Finder. See Finder. [2, 10, 22, 26.] 

 Wynne's Actinometer. See Actinometer. 



X-Ray Machine Apparatus. Apparatus for generating Rontgen 



rays. [26.] 

 XY Chart-Frame. A chart-frame with a transparent xylonite 



top. [13, 15.] 

 XY Rolling Parallel Rule, Field's. A rolling rule with a xylonite 



blade or rule for chart work. [13, 15, 16, 20, 27.] 



