146 



Quekett's Forceps. A long forceps for extracting microscope 



specimens from deep jars. [2, 3, 20, 22.] 

 Quenching Bath Thermometer. See Thermometer. [6, 13, 21.] 

 Quill tant. A special form of sextant enabling a larger angle of 



reflection to be measured than with the ordinary type of 



instrument. [13, 15.] 



Radiation Pyrometers. See Pyrometer. [4, 13, 16, 21, 26.] 

 Radiation Thermometer. See Thermometer. [5, 13, 17, 20, 21, 



26] 



Radio-Activity Measurement Apparatus. For use in connection 

 with an electrometer (q.v.) in measurements and experiments 

 on the radio-activity of substances. It consists of two insu- 

 lated metal plates, the space between them being occupied 

 by a gas which is ionised by the radio-active substance. 

 The two plates are charged to different potentials, and the 

 rate of leakage of electricity across the plates is determined 

 by an electrometer. [4, 26] 



Radiograph. (i) An instrument for the measurement and record 

 of solar radiation. (2) A xylonite or glass plate with circle 

 or semi-circle of degrees on one side and a pencilling surface 

 on the other, for working off two or more observed angles 

 and fixing the ship's position on the chart. [9, 13, 15, 21, 

 25, 26, 28.] 



Radiometer. An instrument for indicating the mechanical effect 

 of radiant energy. It consists essentially of four light vanes, 

 blackened on one side and silvered on the other, mounted 

 on a central pillar so as to revolve freely in a vessel nearly 

 exhausted of air. [13, 17, 26] 



Radiomicrometer. A very sensitive modification or application 

 of the thermopile (q.v.), used for indicating minute changes 

 of radiant heat or temperature. [4, 13, 21.] 



Radio-Micrometer, Boys'. A sensitive radio-micrometer (q.v.) 

 in the form of a modified suspended-coil galvanometer (q.v.), 

 in which the coil consists of a single loop of silver wire with 

 a small bismuth-antimony thermo-couple at its lower end. 

 The radiation to be measured is received on this thermo- 

 couple, the consequent heating of which causes a current to 

 flow through the suspended system. [4] 



Radiophone. An apparatus for the production of sound by 

 the action of luminous or thermal rays. 



Radium Buttons. Containing radium for the treatment of 

 lupus, etc. [3, 26] 



Radium Map-Reader. A magnifier with a radium illuminator 

 for map-reading. [15, 20, 21.] 



Rail Tracing Machine. An instrument for obtaining an accurate 

 tracing of the section of a rail. 



Railway Curves. A set of pearwood curves used by draughtsmen 

 in the setting out of railway lines on plans. [2, 5, 6, 13, 15, 

 17, 21, 24, 26, 27] 



