ra'di-um, a metallic element not unlike table salt in appearance. It was discovered in 1898 at the University of Paris by Professor Curie and wife. Pure radium is seldom prepared, as it is too expensive. This new element is remarkable for the peculiar penetrative power of rays which it gives off. These seem to be of three sorts. They are named after the first three letters of the Greek alphabet, Alpha, Beta, and Gamma. The most powerful are strong enough to affect a photographic plate after passing through a foot of iron. These rays give off but little light, yet pass through all substances, solids, liquids, and gases, having a much greater penetrative power than the so-named X-rays. No method has been found of refracting radium rays. In some respects a piece of radium is like a hot coal. It destroys the growing power of seeds and seems to kill various germs and microbes. Great hopes are entertained that many infectious diseases due to microbes may be checked, if not eradicated, by the use of this new metal. Held near a person's body, its rays penetrate the clothing and burn the flesh, creating ulcers. A pound of radium would kill every one in the vicinity. Some peculiar effects have been noted by scientists. Radium kills the hair of mice, but stimulates the growth of the hair or fur of rabbits when not brought too close. Radium furnishes an absolute test for diamonds. A genuine diamond glows with a phosphorescent light in its presence. A glass tube in which radium is kept acquires an azure tint. A further study of radium is expected to throw much light on phosphorescence, electricity, heat, light, X-rays, in short, all forms of radiant energy. In spite of seeming to give off something, a bit of radium would suffer no appreciable loss of weight, it is said, in a million years. Radium is capable of melting its own weight of ice every hour indefinitely. The separation of radium from the uranium ore, known as pitch-blende, has been undertaken in Vienna. Many tons of ore are required to yield a gram of radium. It is worth $60,000 a gram. It is sold to physicians in vials containing the minute quantity of three one-thousandths of a gram. The price is $216 per vial and radium may be had only by favor at that price. A competent authority, writing in 1910, states that not to exceed a fourth of a pound of radium has been produced as yet. In 1909 ten tons of pitch-blende, from the Bohemian mines at Joachims, were worked over in a laboratory at Vienna at an expense of $10,000. The total find of radium was three grams, about forty-six grains. At this rate a pound avoirdupois would require 1,700 tons of pitch-blende and would cost $1,700,000 for its extraction. It is believed, however, that pitch-blende is less rare than was supposed. The ore has been found at St. Ives, England. Rich traces of radium were found in boring the Simplon Tunnel through the Alps. A Geneva professor insists that the abnormal heat experienced in building the tunnel was due to the presence of radium. Deep sea dredging reveals traces of radium. The work on radio-activity continues to be of surpassing interest. When it was found, a year and a half ago, that helium is one of the decomposition products of radium, it began to appear possible that the elements might not be permanent. The alchemists' dream of transmutation of the elements seemed to be realized. If radium is not a permanent substance, it must be continuously produced from some source. The occurrence of radium in ores of uranium indicated that the latter element, which is also radio-active, might be the mother substance of radium, the atoms of uranium giving, as a decomposition product, the lighter atoms of radium. Several independent researches during the past year have tended to confirm this idea; but the direct attempt to estimate the amount of radium produced in a year from a quantity of a pure uranium compound, gave, if any at all, less than one ten-thousandth of the amount of radium expected. On the other hand, we have the significant suggestion of Ramsay that radium may be formed by synthesis from elements of smaller atomic weight. In accord with this, Ramsay found that by the action of the penetrating rays of radium on glass the latter seemed to be partially transformed into a radio-active body. This may be a synthesis of a radio-active element.-H. A. McCoy in World's Work.