500 



SUBMAKINE CABLE LAYING AND REPAIEING. 



primary, exactly as was No, 1 at first, and by similar trials 

 No. 3 coil is located and its top and bottom ends identified. 

 Then No. 3 is treated as primary to locate No. 4, and so on till 

 the last but one, when all are known. 



The above method assumes that all sections of cable in tank 

 are coiled the same way, but it sometimes happens that an old 

 piece picked up is over-strained and will not coil well in the 



Fig. 278.— Sullivan's Identification Test. 



usual direction. In that case it is coiled the reverse way, and 

 the following extension of the test is necessary to identify the- 

 ends. The charge induced in the secondary coil is stronger at 

 the end nearest the primary and weaker at the end further 

 away on account of the retardation due to inductance. 



If the induced charge is observed on a galvanometer, first at 

 one end of the secondary coil and then at the other, the distant 

 end being free in each instance, the swing will be greater at the 



