162 



SUBMAKINE CABLE LAYING AND EEPAIEING. 



the finger and thumb at the projection H, and slipped into place 

 between the two coiis as in Fig. 80. The mirror is then central 

 and in the axis of the coils. The instrument is enclosed in a 

 heavy soft iron case (shaded in section lines in the figure) which 

 is a shield against magnetic disturbances set up by the move- 

 ment of the ship's iron framework when the vessel rolls. A 



Plan. 



Sectional Elevation through A B' 

 Fig. 79. — Briglit's Reverser. 



small glass window is provided for the rays of light to pass to 

 and from the mirror. There is a stationary controlling magnet 

 under the lower half of the coils, which keeps the magnets and 

 mirror in the same plane as the coils, independently of the ship's 

 position with respect to the earth's magnetism, and also a 

 convenient screw adjustment (by a pinion and rack rods) of two 



