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BELL SYSTEM TECHNICAL JOURNAL 



further, we should say that all this is in accord with physical facts. The 

 inductance per unit length of an infinitely long isolated wire is infinite. 

 The mutual inductance between two parallel wires is also infinite. The two 

 wires are the 'Svindings" of an ideal transformer and a finite impedance is 

 presented only to equal and opposite currents. In the case of wires of finite 

 length the essentially three-dimensional character of the structure manifests 

 itself, and other modes of propagation have to be considered. 



Fig. 1 — Typical equivalent meshes in a circuit representation of continuous media. 



It is evident that the homogeneity of the medium is not a prerequisite for 

 the existence of its network model. Having the values of L and C at our 

 disposal, we can choose them to reflect the dependence of the permeability 

 /Lt and the dielectric constant e on position. 



If we divide the medium into small blocks of volume Ax ^y As, the capaci- 

 tance Cx of the typical capacitor in those branches of the network which are 

 parallel to the x-axis is Cx = t ^y Az/Ax, where € is the dielectric constant. 

 The conductance in parallel with this is Gx = gAyAz/Ax. The inductance 

 of the typical coil in the x^'-plane is L^y = m AxAy/4As. The voltages across 

 the capacitors are E^Ax, EyAy, EzAz, where Ex, Ey, Eg are the electric 

 intensities, that is, the voltages per unit length in the respective directions. 

 The currents in the coils situated in the xy-p\sine are equal to HzAz; simi- 



