184 



SUBMARINE CABLE LAYING AND REPAIRING. 



A beam of light is thrown on to the mirror instrument by 

 means of an oil-lamp and lens. The latter is fixed at one end 

 of a horizontal brass tube, and the tube is shifted until a good 

 sharp reflected ray from the mirror is obtained. The light of 

 the lamp should then be shielded from the eyes by a paper 

 screen, or the lamp for this purpose may be placed in a wooden 

 box without top, and with a small hole in the side opposite 



r-s^-^ 



"immm 



Fig. 93. — Speaking Connections. 



the flame. The edge, and not the flat of the flame, must point 

 towards the mirror. The reflected ray can either be directed 

 horizontally, so as to throw an image on a vertical white screen 

 or the wall, or it may be directed downwards by tilting the 

 mirror instrument as shown. For keeping watch for the ship 

 the light should be projected on to a vertical screen, as it can 

 then be seen from all parts of the room. The manner of tilt- 

 ing the mirror to throw the light on the message pad, as shown 



