Reg Edwards, G4FGQ wrote:
"I have always been under the impression Modes were invented by
academics just to explain by using pictures in their published papers
the pecularities of waves when confined to wave guides."

Could well be. If anyone would like to see some of these pictures, King,
Mimno, and Wing have a well illustrated section beginning on page 243 of
"Transmission Lines, Antennas, and Wave Guides". They even include a
single-wire line, near or far from the earth, in the text.

It isn`t only telegraph which used single-wire transmission lines. In
Tierra del Fuego, there was a single galvanized steel wire running along
the 40-miile long road between Rio Grande and San Sebastian used for
telephone service to the sheep raising "estancias" (stations) along the
route. It was hardly insulated at all. It must have worked, but we never
imitated nor tried to gain access. We interfered with the estancias as
little as possible. Drilling for oil was imposition enough. In return we
were the finders, producers, refiners, and marketers of petroleum
products and natural gas on the Argentine side of the island.

Best regards, Richard Harrison, KB5WZI