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Page:Popular Science Monthly Volume 48.djvu/853

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THE X RAYS.

putes to arbitration and England eight, and of these four were between England and the United States." The writer, W. J. Gennadius, quotes two very apposite declarations, one by General Grant, and one by that experienced and sagacious statesman, the late Earl Russell. Grant's words are, "Though I have been trained as a soldier, and have participated in many battles, there never was a time when, in my opinion, some way could not have been found to prevent the drawing of the sword." And Earl Russell's: "On looking at the wars which have been carried on during the last century, and examining into the causes of them, I do not see one in which, if there had been proper temper between the parties, the questions in dispute might not have been settled without recourse to arms." These declarations are worth reflecting on. The proviso introduced by Earl Russell is particularly significant: "If there had been proper temper between the parties." That is what is wanted, "proper temper." It resolves itself thus into a question of national righteousness. The cynic may laugh at the conclusion; but those who are not cynics will venture to believe that the problem is not hopeless.

 

THE X RAYS.
By JOHN TROWBRIDGE,

RUMFORD PROFESSOR AND LECTURER ON THE APPLICATION OF SCIENCE TO THE USEFUL ARTS, HARVARD UNIVERSITY.

SINCE the publication of Hertz's paper on the penetration of thin sheets of metal, notably aluminum, by the cathode rays, interest in the remarkable phenomena investigated first by Prof. Crookes has been reawakened to a marked degree; and most physicists during the past five years have regarded the subject of cathode rays as the most important one in electricity. In 1893 Lenard succeeded, by means of a Crookes tube provided with a small aluminum window, in detecting the cathode rays outside the tube in the air space of an ordinary room. He used paper disks covered with a very fluorescent substance, which became luminous when the cathode rays struck them; and he also succeeded in showing photographic effects of the rays. Now Röntgen, by the use of ordinary dry plates and without the use of an aluminum window, has taken photographs through wood and through the human hand by means of what he terms the X rays, which he supposes are excited either in the glass walls of the Crookes tube or in the media outside the tube by means of the cathode rays.

We see, therefore, that the literature of the subject must be