On this day in 1895 Alexander Popov stood before the Russian Physical and Chemical Society in St Petersburg and presented a paper on his invention, a wireless device for detecting the radio noise from lightning. The detector made use of a so-called coherer, a tube containing two closely spaced electrodes; in the presence of radio waves, iron filings placed between the electrodes cohere, thereby establishing a conducting path for current to flow. Popov concluded his paper with a prediction: "I can express my hope that my apparatus will be applied for signaling at great distances by electric vibrations of high frequency, as soon as there will be invented a more powerful generator of such vibrations." Just a few months later, Guglielmo Marconi demonstrated wireless telegraphy.
