Most ships are provided with syntonic receivers which are tuned to long distance transmitters, and are capable of receiving messages up to distances of 3,000 miles or more. Wireless communication between Europe and America is no longer a possibility but an accomplishment, though as yet the system has not been put on a general business basis. [Footnote: As we go to press a new record has been established in wireless transmission. Marconi, in the Argentine Republic, near Buenos Ayres, has received messages from the station at Clifden, County Galway, Ireland, a distance of 5,600 miles. The best previous record was made when the United States battleship _Tennessee_ in 1909 picked up a message from San Francisco when 4,580 miles distant.] CHAPTER III RADIUM Experiments of Becquerel--Work of the Curies--Discovery of Radium--Enormous Energy--Various Uses. Early in 1896 just a few months after Roentgen had startled the scientific world by the announcement of the discovery of the X-rays, Professor Henri Becquerel of the Natural History Museum in Paris announced another discovery which, if not as mysterious, was more puzzling and still continues a puzzle to a great degree to the present time. Studying the action of the salts of a rare and very heavy mineral called uranium Becquerel observed that their substances give off an invisible radiation which, like the Roentgen rays, traverse metals and other bodies opaque to light, as well as glass and other transparent substances. Like most of the great discoveries it was the result of accident. Becquerel had no idea of such radiations, had never thought of their possibility.