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BELL SYSTEM TECHNICAL JOURNAL 



The armoring was then assumed to be replaced by sea water, and 

 the resistance and inductance of the cable were calculated from (33). 



The results of the calculations are shown in the curves of Fig. 3. 



It is evident from these curves that the effect of the iron armoring 

 is to increase considerably the impedance of the return path. The 



Z5 



50 

 Fig. 3 



100 



physical explanation of this fact is that the iron acts as a shield to 

 screen from the sea water the electromagnetic effects of the current 

 flowing in the cable conductor. Energy is dissipated in the armoring 

 and is prevented from spreading out through the surrounding medium. 

 The assumption that the armor wires could be replaced by a solid 

 cylinder of iron is, therefore, subject to question, since it is possible 

 that the larger surface area of the assemblage of armor wires, and 

 the gaps between these wires may be effective in diminishing the 

 energy dissipated in the armoring and consequently diminishing the 

 screening effect. This problem is investigated in the following section. 



IV 



The physical system under consideration is shown schematically 

 in cross-section in Fig. 4, and consists of an insulated conductor and 



