100 



Gun Pit Register. An arrangement designed for keeping the 

 necessary records of field artillery battery in a gun pit. 



Gunner's Callipers. See Callipers. [1, 27.] 



Gunner's Level. See Gunner's Perpendicular. 



Gunner's Perpendicular. An instrument for determining the 

 true line of sight of a gun. 



Gunner's Quadrant. See Quadrant. 



Gunter's Chain. A measuring chain (q.v.) used in surveying, 

 66 ft. or 4 rods long, divided into 100 links. [5, 13, 15, 16, 

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



Gunter's Quadrant. See Quadrant. [13.] 



Gunter's Scale. A wooden scale. 2 ft. long, on one side of which 

 are marked scales in equal parts of chords, rhombs, etc., 

 and on the other side, scales of logarithms of these various 

 parts, by means of which many problems in surveying and 

 navigation may be solved mechanically, by means of 

 dividers alone. [13, 15, 17, 18, 20, 21, 27.] 



Gyroscope. A rotating wheel with a free suspension mounted in 

 a ring or rings, for demonstrating the dynamics of rotating 

 bodies, the composition of rotation, etc. See Gyroscope 

 Compass. [13, 17, 19, 26.] 



Gyroscope Compass. An important application of the gyroscope 

 by means of which the true course of a ship is indicated. 

 The instrument is not affected by the magnetic force of the 

 ship. It consists of a heavy disc, mounted with a free 

 suspension and driven at a high speed by electrical power. 

 The centrifugal force of the earth causes this disc to revolve 

 in or coincide with the circle of latitude the ship is on. A 

 dial, which is mechanically connected with the discs, has 

 the points and diagram of the mariner's compass marked 

 on its face and from it is indicated the true course the ship 

 is on. Secondary dials are electrically connected to indicate 

 at other stations on the ship. It is used principally on 

 warships and submarines. [13, 15, 26.] 



Gyrostat. A modification of the gyroscope. It consists essent- 

 ially of a fly-wheel mounted inside a rigid case, to which is 

 attached a thin flange of metal for supporting the instru- 

 ment. It is used in studying the dynamics of rotating 

 bodies. 



Gypsum Plates. Thin parallel plates of gypsum (selenite) for 

 retarding the light of a polariscope. [3, 22, 26.] 



Hadley Dial. See Dial. [13, 15, 18, 21, 27.] 

 Hadley's Quadrant. See Quadrant. [13, 15.] 

 Haedromograph. An instrument for registering the velocity of 



the blood. 

 Hsemachrometer. An apparatus for measuring the amount of 



haemaglobin in a fluid by comparing it with a solution of 



known strength and normal colour. [2.] 



