Page "Anode" Paragraph 9

The use of ' East ' to mean the ' in ' direction ( actually ' in ' → ' East ' → ' sunrise ' → ' up ') may appear contrived.

Previously, as related in the first reference cited above, Faraday had used the more straightforward term " eisode " ( the doorway where the current enters ).

His motivation for changing it to something meaning ' the East electrode ' ( other candidates had been " eastode ", " oriode " and " anatolode ") was to make it immune to a possible later change in the direction convention for current, whose exact nature was not known at the time.

The reference he used to this effect was the Earth's magnetic field direction, which at that time was believed to be invariant.

He fundamentally defined his arbitrary orientation for the cell as being that in which the internal current would run parallel to and in the same direction as a hypothetical magnetizing current loop around the local line of latitude which would induce a magnetic dipole field oriented like the Earth's.

This made the internal current East to West as previously mentioned, but in the event of a later convention change it would have become West to East, so that the East electrode would not have been the ' way in ' any more.

Therefore " eisode " would have become inappropriate, whereas " anode " meaning ' East electrode ' would have remained correct with respect to the unchanged direction of the actual phenomenon underlying the current, then unknown but, he thought, unambiguously defined by the magnetic reference.

In retrospect the name change was unfortunate, not only because the Greek roots alone do not reveal the anode's function any more, but more importantly because, as we now know, the Earth's magnetic field direction on which the " anode " term is based is subject to reversals whereas the current direction convention on which the " eisode " term was based has no reason to change in the future.