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JUN 20 1917

TRANSFERRED TO

HARVARD COLLEGE LIBRARY

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Courtesy of New York Tribune.

PROFESSOR AND MADAME CURIE, THE DISCOVERERS OF RADIUM. Whose researches have opened up the great field of subatomic energy.

The

Technical World

Volume I

MARCH, 1904

Number I

T

RADIUM

THE REVOLUTIONARY ELEMENT

By ROBERT A. MILLIKAN, Ph. D.
Assistant Professor of Physics,
University of Chicago

one

HE past eight years have been marked by a number of epochmaking discoveries in physics. Most of these recent additions to the range of scientific knowledge have been grouped about the general subject of radiation, discoveries of new forms of radial energy having followed another in such rapid succession that it is difficult even for a physicist to keep posted on them all. As a result of these achievements, important progress has been made toward the solution of one of the most fundamental questions that can be asked in science-the question as to the nature and constitution of matter.

The Discovery of X-Rays

-a radiation which was like light in that it produced an effect upon a sensitized photographic plate, but was wholly unlike light, first, in that it was invisible, and second, in that it was able to pass easily through many substances opaque to ordinary light, such, for example, as cardboard, wood, leather, and notably the flesh of the human hand. This discovery would probably have attracted little attention outside of academic circles had it not been for this last-mentioned remarkable property; but the idea of obtaining photographs of the skeleton of a living being was so startling, so uncanny at that time, to the average mind, that the discovery at once took hold of the popular imagination and for at time monopolized the attention even of the scientific world. Scores of scientists in all countries dropped at once their pending researches, and began to experiment upon these strange new rays, which Röntgen had provisionally named X-rays because their nature was still problematical. A surprisingly small amount of new knowledge concerning the mysterious nature of the X-rays themselves resulted from all this research, and even today they are almost as much an unknown quantity as when Röntgen made his first announcement. HARYAND COLLEGE LIBRAR!

The discovery of X-rays is to be regarded as the starting-point of this epoch of investigation in the field of radio-activity. It was in the Christmas season of 1895-96 that Professor Röntgen of the University of Würzburg, Bavaria, exhibited to the Physical Society of Berlin his first X-ray photographs and announced to the public the discovery that has made his name a household term the world over. These photographs showed that some sort of radiation was emitted from a vacuum bulb through which an electrical discharge was passing

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