10 



SUBMARINE CABLE LAYING AND REPAIRING, 



left a back pull of 101b., tending to stop the wire paying out 

 further. The mean speed of descent was only about 65 fathoms 

 per minute. 



The drum was made very light, of thin sheet galvanised 

 iron, to give it small inertia and prevent its shooting the wire 

 forward when the weight touched bottom. The auxiliary 

 pulley B for reeling-in was driven through speed-reducing gear 

 by the pinion A connected to the steam engine, and the wire 

 drum was driven by a band from B, a lever and tightening 

 gear being attached. The pulley C turned in any direction on 

 a centre coinciding with the horizontal portion of the wire, and 



Wire Drum in position 

 for hauling in. 



Fig. 7. — Silvertown Sounding Machine. 



was therefore free to take up a position agreeing with any 

 direction in which the wire might stream out from the ship. 

 As the wire came up it was dried by passing through a block 

 of indiarubber and oiled by passing through a brush saturated 

 with lard oil, thus keeping it in good condition. 



This machine is now superseded by machines adapted for the 

 use of heavier sinkers and greater speeds of descent. As the 

 moment of striking bottom can now be easily detected when the 

 line is run out at a speed of 100 to 150 fathoms per minute, it 

 not of importance to have the sounding machine drum of light 

 construction, and the system described above of adding weights 



