408 



BELL SYSTEM TECHNICAL JOURNAL 



of the typical transoceanic cable is submerged, only the extremely low 

 frequency components of the surface disturbance are encountered to 

 an appreciai)lc degree. In the vicinity of the terminals, however, 

 where the water is comparatively shallow, the cable is exposed to the 

 higher frequency components of the disturbances, and it is usually in 

 these sections that the greater part of the most troublesome disturb- 

 ances is picked up. This is especially true in localities where the zone 

 of shallow water extends a considerable distance from shore. Such a 

 case is shown in Fig. 4, which represents a typical profile of the ocean 

 bottom for the shallow water portion of a cable terminating at New 

 York. 



DISTANCE FROM NEW YORK- NAUTICAL MILES 







100 



200 



300 



t! 400 



liJ 

 UJ 



i 



° 600 



500 



700 



UJ 



^ 800 



900 

 1000 



120 



FIG. 4 



The phenomena attending the induction of an electromotiv^e force in 

 the cable conductor by an electromagnetic field are rather complicated 

 and difficult of exact computation. In the first place, on account of 

 the change in electrical constants in passing from sea water to ocean 

 bottom, the electric and magnetic field intensities in the neighborhood 

 of the cable are somewhat different than indicated by equation (1). 

 The influence of this factor upon the final result is in general small 

 compared with that of the other factors that we are considering, and, 

 on account of our lack of knowledge concerning the electrical character- 

 istics of the ocean bottom, theoretical discussion would be of little 

 practical value. A second factor is the shielding effect of the armor 

 wires and metallic tapes surrounding the core. No attempt will be 

 made in the present paper to work out an analytical solution of this 



