On December 21, 1902, from a station at Glace Bay, Nova Scotia, Marconi sent the first message by wireless to England announcing success to his colleagues.
The following January from Wellsfleet, Cape Cod, President Roosevelt sent a congratulatory message to King Edward. The electric waves conveying this message traveled 3,000 miles over the Atlantic following round an arc of forty-five degrees of the earth on a great circle, and were received telephonically, by the Marconi magnetic receiver at Poldhu.
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.
In the early days of the Roentgen rays there were many facts which suggested that phosphorescence had something to do with the production of these rays It then occurred to several French physicists that X-rays might be produced if phosphorescent substances were exposed to sunlight. Becquerel began to experiment with a view to testing this supposition. He placed uranium on a photographic plate which had first been wrapped in black paper in order to screen it from the light. After this plate had remained in the bright sunlight for several hours it was removed from the paper covering and developed. A slight trace of photographic action was found at those parts of the plate directly beneath the uranium just as Becquerel had expected. From this it appeared evident that rays of some kind were being produced that were capable of passing through black paper. Since the X-rays were then the only ones known to possess the power to penetrate opaque substances it seemed as though the problem of producing X-rays by sunlight was solved. Then came the fortunate accident. After several plates had been prepared for exposure to sunlight a severe storm arose and the experiments had to be abandoned for the time being. At the end of several days work was again resumed, but the plates had been lying so long in the darkroom that they were deemed almost valueless and it was thought that there would not be much use in trying to use them. Becquerel was about to throw them away, but on second consideration thinking that some action might have possibly taken place in the dark, he resolved to try them. He developed them and the result was that he obtained better pictures than ever before. The exposure to sunlight which had been regarded as essential to the success of the former experiments had really nothing at all to do with the matter, the essential thing was the presence of uranium and the photographic effects were not due to X-rays but to the rays or emanations which Becquerel had thus discovered and which bear his name.
There were many tedious and difficult steps to take before even our present knowledge, incomplete as it is, could be reached. However, Becquerel's fortunate accident of the plate developing was the beginning of the long series of experiments which led to the discovery of radium which already has revolutionized some of the most fundamental conceptions of physics and chemistry.
It is remarkable that we owe the discovery of this wonderful element to a woman, Mme. Sklodowska Curie, the wife of a French professor and physicist. Mme. Curie began her work in 1897 with a systematic study of several minerals containing uranium and thorium and soon discovered the remarkable fact that there was some agent present more strongly radio-active than the metal uranium itself. She set herself the task of finding out this agent and in conjunction with her husband, Professor Pierre Curie, made many tests and experiments. Finally in the ore of pitchblende they found not only one but three substances highly radio-active. Pitchblende or uraninite is an intensely black mineral of a specific gravity of 9.5 and is found in commercial quantities in Bohemia, Cornwall in England and some other localities. It contains lead sulphide, lime silica, and other bodies.