Boys' Second Book of Inventions. Ray Stannard Baker

in certain cases of blindness. I held a tube of radium to my closed eye and was conscious of the sensation of light; the same sensation was present when the tube was held to my temple, thus showing that the radium has an effect on the optic nerve. A little blind girl in New York, who had never had the sensation of light, began to see a little after one treatment with radium, and experiments are still going on, but cautiously, for fear that injuries may result.

      We now come to the fascinating story of the discovery and manufacture of radium. It has long been known that certain substances are phosphorescent; that is, under the proper conditions they glow without apparent heat. Everybody has seen "fox-fire" in the damp and decaying woods—a cold light which scientists have never been able to explain.

      To M. Henri Becquerel of the French Institute is generally given the credit for having begun the real study of radio-activity, although, as in every great discovery and invention, many other scientists and practical electricians had paved the way by their investigations. In 1896 M. Becquerel was conducting some experiments with various phosphorescent substances. He exposed some salts of the metal uranium to the sunlight until they became phosphorescent, and then tried their effect upon a photographic plate.

      It rained, and he put the plate away in a drawer for several days. When he developed it he was surprised to find on it a better image than sunlight would have made. And thus, by a sort of accident, he led up to the discovery of the Becquerel rays, so called.

      Uranium is extracted from a metal or ore called uranite by mineralogists, and popularly known as pitch-blende. Every young college student who has studied geology or chemistry has heard of pitch-blende.

      Two years after Becquerel's discovery of the radio-activity of uranium Professor Pierre Curie and Madame Curie, of Paris, made the discovery that some of the samples of pitch-blende which they had were much more powerful than any uranium that they had used.

      Was there, then, something more powerful than uranium within the pitch-blende? They began to "boil down" the waste rock left at the uranium mines, and found a strange new element, related to uranium but different, to which Madame Curie gave the name polonium, after her native land, Poland.

      Dr. Danlos Treating a Lupus Patient with Radium at the St. Louis Hospital, Paris.

      Then they did some more boiling down, and succeeded in isolating an entirely new substance, and the most radio-active yet discovered—radium. Shortly after that Debierne discovered still another radio-active substance, to which he gave the name actinium.

      Thus three new elements were added to the list of the world's substances, and the most wonderful of these is radium. In a day, almost, the Curies became famous in the scientific world, and many of the greatest investigators in the world—Lord Kelvin, Sir William Crookes, and others—took up the study of radium.

      Very rarely have a man and woman worked together so perfectly as Professor Curie and his wife. Madame Curie was a Polish girl; she came to Paris to study, very poor, but possessed of rare talents. Her marriage with M. Curie was such a union as must have produced some fine result. Without his scientific learning and vivid imagination it is doubtful if radium would ever have been dreamed of, and without her determination and patience against detail it is likely the dream would never have been realised.

      One of the chief problems to be met in finding the secrets of radium is the great difficulty and expense, in the first place, of getting any of the substance to experiment with. The Curies have had to manufacture all they themselves have used. In the first place, pitch-blende, which closely resembles iron in appearance, is not plentiful. The best of it comes from Bohemia, but it is also found in Saxony, Norway, Egypt, and in North Carolina, Colorado, and Utah. It appears in small lumps in veins of gold, silver, and mica, and sometimes in granite.

      Comparatively speaking, it is easy to get uranium from pitch-blende. But to get the radium from the residues is a much more complicated task. According to Professor Curie, it is necessary to refine about 5,000 tons of uranium residues to get a kilogramme—or about 2.2 pounds—of radium.

      It is hardly surprising, therefore, considering the enormous amount of raw material which must be handled, that the cost of this rare mineral should be high. It has been said that there is more gold in sea-water than radium in the earth. Professor Curie has an extensive plant at Ivry, near Paris, where the refuse dust brought from the uranium mines is treated by complicated processes, which finally yield a powder or crystals containing a small amount of radium. These crystals are sent to the laboratory of the Curies where the final delicate processes of extraction are carried on by the professor and his wife.

      And, after all, pure metallic radium is not obtained. It could be obtained, and Professor Curie has actually made a very small quantity of it, but it is unstable, immediately oxidised by the air and destroyed. So it is manufactured only in the form of chloride and bromide of radium. The "strength" of radium is measured in radio-activity, in the power of emitting rays. So we hear of radium of an intensity of 45 or 7,000 or 300,000. This method of measurement is thus explained. Taking the radio-activity of uranium as the unit, as one, then a certain specimen of radium is said to be 45 or 7,000 or 300,000 times as intense, to have so many times as much radio-activity. The radium of highest intensity in this country now is 300,000, but the Curies have succeeded in producing a specimen of 1,500,000 intensity. This is so powerful and dangerous that it must be kept wrapped in lead, which has the effect of stopping some of the rays. Rock-salt is another substance which hinders the passage of the rays.

      English scientists have devised a curious little instrument, called the spinthariscope, which allows one actually to see the emanations from radium and to realise as never before the extraordinary atomic disintegration that is going on ceaselessly in this strange metal. The spinthariscope is a small microscope that allows one to look at a tiny fragment of radium supported on a little wire over a screen.

      Radium as a Test for Real Diamonds.

      At the approach of Radium pure gems are thrown into great brilliancy, while imitations remain dull.

      The experiment must be made in a darkened room after the eye has gradually acquired its greatest sensitiveness to light. Looking intently through the lenses the screen appears like a heaven of flashing meteors among which stars shine forth suddenly and die away. Near the central radium speck the fire-shower is most brilliant, while toward the rim of the circle it grows fainter. And this goes on continuously as the metal throws off its rays like myriads of bursting, blazing stars. M. Curie has spoken of this vision, really contained within the area of a two-cent piece, as one of the most beautiful and impressive he ever witnessed; it was as if he had been allowed to assist at the birth of a universe. Radium emits radiations, that is, it shoots off particles of itself into space at such terrific speed that 92,500 miles a second is considered a small estimate. Yet, in spite of the fact that this waste goes on eternally and at such enormous velocity, the actual loss sustained by the radium is, as I have said, infinitesimal.

      We now come to one of the most interesting phases of the whole subject of radium—that is, the influence which its strange rays have upon animal life. Mr. Cleveland Moffett, to whom I am indebted for the facts of the following experiments, recently visited M. Danysz, of the Pasteur Institute in Paris, who has made some wonderful investigations in this branch of science. M. Danysz has tried the effect of radium on mice, rabbits, guinea-pigs, and other animals, and on plants, and he found that if exposed long enough they all died, often first losing their fur and becoming blind.

      But the most startling experiment performed thus far at the Pasteur Institute is one undertaken by M. Danysz, February 3, 1903, when he placed three or four dozen little larvæ that live in flour in a glass flask, where they were exposed for a few hours to the rays of radium. He placed a like number of larvæ in a control-flask, where there was no radium, and he left enough flour in each flask for the larvæ to live upon. After several weeks it was found that most of the larvæ in the radium flask had been killed, but that a few of them had escaped the destructive action of the rays by crawling away to distant corners of the flask,