Скачать или смотреть Sir Oliver Lodge on dialectric and incompresible nature of the medium 1907

One of the fundamental experimental facts concerning electricity is that it is impossible to charge an insulated chamber by performing electrical experiments in its interior. Electrical machines inside a conducting chamber and electroscope outside, or vice versa, are perfectly independent of each other. This may be expressed by saying that the field of force outside a conductor, and the field of force inside, are quite independent; that there is entire dislocation of every line of force at the conductor; that a closed conductor acts as a perfect electrostatic screen.

A second fundamental experimental fact is that if a charge be in any way communicated to, or even passed into the interior of, a hollow conductor, the same precise quantity at once appears on the outside; and a variant of this is that if the outside skin of a conductor be peeled off, all charge is removed with that outer skin: no trace remaining below it.

These two facts lead us to say that electricity behaves like an incompressible fluid of which all space is precisely full; a fluid moreover which cannot be manufactured but only moved about. For think of a closed chamber in the sea with pumps inside it. So long as there is no communication through the walls, all that the pumps could do would not result in a trace more liquid in the vessel than there was at first. The vessel cannot be thus charged. But now suppose some water to be pumped from the outside into the interior, through a suitable opening; how could it be done? The vessel being already by hypothesis quite full, either the water must be compressible, in which case the extra charge would exist uniformly throughout the enclosed space; or the vessel must be expansible or porous, in which case the extra charge is not found in the original space at all, but outside it. Whatever extra quantity was pumped into the original space, that same amount precisely would instantly appear outside it; and this is what happens with electricity (§ 4).