Alluding to a well-known anecdote relating to Christopher Columbus, Sir W.Preece very justly said: "The forerunners and rivals of Marconi no doubt knew of the eggs, but he it was who taught them to make them stand on end." This judgment will, without any doubt, be the one that history will definitely pronounce on the Italian scholar.
Sec.

7 The apparatus which enables the electric waves to be revealed, the detector or indicator, is the most delicate organ in wireless telegraphy.

It is not necessary to employ as an indicator a filings-tube or radio-conductor.

One can, in principle, for the purpose of constructing a receiver, think of any one of the multiple effects produced by the Hertzian waves.

In many systems in use, and in the new one of Marconi himself, the use of these tubes has been abandoned and replaced by magnetic detectors.
Nevertheless, the first and the still most frequent successes are due to radio-conductors, and public opinion has not erred in attributing to the inventor of this ingenious apparatus a considerable and almost preponderant part in the invention of wave telegraphy.
The history of the discovery of radio-conductors is short, but it deserves, from its importance, a chapter to itself in the history of wireless telegraphy.