If any sensible current flows through this insulator the galvanometer will show a deflection.
Theoretically this requires an infinite plate; or a perfect heat insulator, so that the lateral flow can be prevented or rendered negligible.
First as regards the transmitting part, one essential element is the antenna, aerial, or air wire, which may take a variety of forms. It may consist of a single plain or stranded copper wire upheld at the top by an insulator from a mast, chimney or building.
Of the ends of the insulator and the current flowing through it, that is, by its insulation resistance.
It is a well-ascertained fact that the insulator, gutta-percha, is, when kept under water, practically imperishable, so that it is only the original strength of the sheathing wires and the deterioration allowable in them that have to be considered.