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BELL SYSTEM TECHNICAL JOURNAL 



layers may be determined. Small scale models, having the proper 

 propagation constant, could advantageously be used in determining 

 the alternating-current impedances for uniform earth resistivity or 

 any assigned distribution of resistivity. 



REACTANCE AT 25 CYCLES - OHMS 



Fig. 11 — Comparison of measured mutual reactances at 25 and 60 cycles. A right 



line with the slope 2.0 fits the point somewhat better than a line with the slope 2.4 



which corresponds to the ratio of the frequencies 



10. Summary 



Formulas for the direct-current mutual resistances and mutual 

 inductances for grounded circuits on the assumption of uniform 

 earth resistivity have been derived and useful diagrams prepared. 

 The applicability of these results as a first approximation to many 

 practical alternating-current cases has been shown. 



If, as I hope, this paper is free from ambiguities and errors, it is 

 due to a thorough revision by Mr. R. M. Foster; and I am indebted 



