On 7 May 1895, Aleksandr Popov demonstrates before the Russian Physical and Chemical Society in St. Petersburg an electromagnetic wave receiver based on a metal-filings coherer, antenna, and relay, initially conceived as a lightning-storm detector. In March 1896 he uses it to transmit the first real message in Morse code over 250 meters. Popov worked under a Russian Navy non-disclosure clause, which prevented him from patenting his invention and worked against him relative to Marconi's later recognition.