186 



SUBMARINE CABLE LAYING AND REPAIRING. 



writer. The instrument is a great favourite with, old cable 

 operators, and there is certainly a fascination about the noise- 

 less movement of the spot of light. The recorder has a motor 

 or clockwork to propel the slip and a vibrator for the siphon, all 



Fig. 94. — Speaking Mirror. 



of which gives it the character of a machine, and even when no 

 signals are passing it seems to be at work. The mirror, on the 

 other hand, gives out signals absolutely without a sound, and in 

 the quiet of a cable-house or at dead of night the streak of light 

 appears to possess life as the words come out, and it seems 



Fig. 95. — Tube and MiiTor and Iron Core. 



almost to be speaking like a human companion. The instru- 

 ment is represented in Fig. 94, and consists simply of a coil 

 wound to a resistance of 1,000 to 2,500 ohms, mounted on a 

 wooden stand. The mirror is suspended at one end of a brass 

 tube (Fig. 95), fitting loosely into the centre of the coil, 



