At the end of the nineteenth century Édouard Branly discovered that the electrical resistance of a granular metallic conductor could drop by several orders of magnitude when excited by the electromagnetic field emitted by a distant electrical spark [ ]. Despite the fact that this effect was used to detect radio waves in the early days of wireless telegraphy and more recently, studied in the field of granular materials, no satisfactory explanation of the physical origin of the effect has been proposed. In this contribution, we relate the Branly effect to the induced tunnelling effect first described by François Bardou and Dominique Boosé [ ].
