A D V E N T U R E S   in   C Y B E R S O U N D

Wireless did not spring full grown from the brain of Guglielmo Marconi, as many people suppose. It was instead the logical culmination of a long series of achievements by many scientists and inventors.

Developments in electricity and magnetism date back to Thales of Miletus, who more than twenty-five hundred years ago observed that a piece of amber, rubbed with a cloth, would attract certain light(weight) objects. (The word electricity itself is from the greek word for amber, electron.) Although the bridge across the ages from Thales to Marconi is marked by many notable achievments, actual radio communication is the work of a few brilliant men, whose labours can be traced from the first half of the nineteeth century.

Michael Faraday one of the great original thinkers of all time was one of those men... Faraday's electrical experiments began in 1820. By 1831 he was able to demonstrate that electricity could be produced by magnetism... James Maxwell's 'Treatise on Electricity and Magnetism' published in 1873 (in part, theorised that)...the changing electric and magnetic fields in space would produce electromagnetic waves. It would be fifteen years later in 1888 that Heinrich Hertz would prove the existance of Maxwell's electromagnetic waves... (and another four years) before anyone suggested that they might be used to communicate through space.

(In 1892,) writing in the London Fortnightly Review, William Crookes suggested that once a simpler and more certain method of generating waves of any desired wavelength could be found, together with more sensitive receivers that could respond selectively to desired wavelengths, it might be possible to communicate with them...Two friends "could thus communicate... by timing the impulses to produce long and short intervals in the ordinary Morse Code."

The next step was made by Edouard Branly who observed that the resistance of a tube filled with partices of metal changed when subjected to either alternating or direct currents. Branly next found that the tube's resistance also dropped in the vicinity of a lightning discharge. He then placed his tube in a circuit containing a battery and a galvanometer, and found that no current flowed in it. But when he placed an induction coil spark generator at distances up to 35 feet from the circuit, and produced sparks with his generator, he observed that the current flowed in the circuit, as indicated by the galvanometer. Branly reported his findings to the French Academy in 1891, but attached no particular significance to the phenomonon.

It was not until 1894 that Oliver Lodge demonstrated it as a detector of Hertzian Waves. He named Branly's device a coherer because the metal particles cohered under the influence of the waves.

Source: Leinwoll, Stanley, From Spark to Satellite

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