"R.Wieser"  wrote:

> You know, that sounds a lot more believable than what I thought I gleaned
> from the article : "In order to keep the disturbances of the magnetic
> compasses of passing ships as small as possible, a bipolar cable was used".

The keyword here being "bipolar" in contrast to a monopolar cable with
return currents passed through the water (e.g.
https://en.wikipedia.org/wiki/Baltic_Cable )

A DC current produces a magnetic field around the wire. In a bipolar cable,
both fields mostly cancel each other out.

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