106 SUBMAKINE CABLE LAYING AND EEPAIKING. 



a condenser and earth, the condenser usually being equal in 

 capacity to 1 mile of cable. Current is applied for five 

 minutes, during which time the leakage from core to plate 

 accumulates and charges the condenser. The discharge of the 

 condenser is then taken by pressing the key and reading the 

 throw on the galvanometer. This result is compared -with a 

 length of perfect core tested in the same manner. If the 

 length of core equivalent to the joint is greater than the limit 

 allowed or specified the joint is rejected and remade. A good 

 joint is equivalent to about 12 in. of perfect core. In these tests 

 the insulation of the trough has to be carefully measured and 

 allowed for. 



The sheathing of a cable is now always put on with a left- 

 handed lay — that is, with the wires running from the observer 

 towards the left hand looking along the line of cable. This, 

 however, was not so when sheathings were first applied, but 

 was adopted afterwards as the result of experience. The firms of 

 Messrs. R. S. Newall and Co. and Messrs. Glass and Elliot, by 

 whom iron sheathings were first applied to cables, were manu- 

 facturers of colliery wire rope, and the custom of making pit 

 rope and other ropes generally with a right-handed lay was 

 naturally followed at first in the sheathing of submarine 

 cables. It was not long however before it was found that 

 cable sheathed with a right-handed lay would not coil down in 

 tank when the coiler ran round with the cable in his right 

 hand, as was most natural and easy. 



It was therefore necessary to reverse the direction of coiling, 

 and this obliged the coiler to run round the tank in the 

 opposite direction with the cable in his left hand, which was 

 awkward. The conditions, in fact, of coiling ordinary rope 

 and submarine cable are not the same. When rope is coiled 

 flat, say on a deck, the coiling is commenced at the inner end 

 and continued round and round away from the ceucre, but 

 when cable is coiled in a tank the coiling is commenced round 

 the side of the tank and continued inwards towards the centre. 



Messrs. Glass and Elliot first met the conditions required in 

 coiling cable in tanks by applying a left-handed lay to the 

 sheath, which overcame the diflBculties mentioned above and 

 has since been generally adopted. The two lays are sketched 

 in Fig. 52. 



