302 SUBMARINE CABLE LAYING AND EEPAIEING. 



on spindles at right angles to each other. The leads are placed 

 with the vertical pulley on the side towards which the cable 

 bears, the course of the cable over deck not being straight 

 along the whole distance. Guides are provided on either side 

 of the rollers to keep the cable from shifting. 



Surface currents and tides have a marked effect on rate of 

 paying out. The rotometer may register as much as eight 

 knots of cable going out per hour, if the set of the current is 

 with the ship. This is, of course, not too great a speed if the 

 current is carrying the ship along, say, three knots over the 

 ground, independently of her own speed of five knots through 

 the water ; but the effect must not be mistaken for paying out 

 too much slack and strain thrown on the cable by setting up 

 the brake. Under ordinary conditions, when the tide or 

 current is not flowing in the ship's course, the fact of 

 eight knots leaving the ship when she is only moving five 

 would, of course, mean 50 per cent, more slack than necessary, 

 and great waste of cable. The cost of cable when new being 

 over £200 per mile, it is an important matter to pay out only 

 just what slack is necessary for laying without strain, and for 

 repairs. The speed of ship through the water is ascertained by 

 the log, but this gives no idea of her speed over the ground as 

 affected by tide or leeway ; and while the direction and force of 

 the tides are generally known, and the ship's course can conse- 

 quently be kept straight over ground by making due allowance, 

 it is a more difficult matter to make any correct observation of 

 the surface currents, unless any land is in view to go by. 



The strain or tension on cable indicated by the dynamo- 

 meter as ship pays out should represent a little less than the 

 weight of cable in water corresponding to the depth, and should 

 increase with the depth. With light cables in 1,000 fathoms 

 the strain allowed is about 12cwt. to 15 cwt. The brakesman 

 only alters the brake if the ship is pitching much, in which case 

 he eases it a little as ship's stern rises. All other adjustments 

 are made by adding weights or tightening the screws on the 

 brake-strap, accordiug to the design of brake. 



Repairlng-steamers generally have not' the deck room for sepa- 

 rate aft paying-out gear, and do all their paying out from the for- 

 ward drums, taking the cable back over the stern or bow sheaves as 

 most convenient. Large repairing-vessels are sometimes fitted, 



