CHAPTER XII
Miscellaneous Researches on Roentgen Rays.
151. Pupin and Swinton’s Experiment. Sciagraphic Plates Combined with Fluorescent Salts. The Elect., Lon., Apr. 24, ’96.—Prof. Pupin, of Columbia College (Electricity, N.Y., Feb. 12, ’96—the author saw him use it Feb. 7, ’96—), was among the first, and probably actually the first, to lessen the time of exposure by a fluorescent screen. Prof. Salvioni also worked in this direction at an early date. Prof. Swinton reported some details in the matter, and he was able to obtain a sciagraph of the bones of the hand in less than 10 seconds, with a moderately excited discharge tube, whereas, without the screen the time was two minutes. He experimented first with barium platino cyanide, but the results referred to were obtained with calcic tungstate, finely ground, and made up into paste by means of gum, and dried. He spread the same upon a celluloid sheet which was placed with the celluloid side against the photographic film. The difficulty experienced first was in the formation of spots on the negative, because some of the crystals fluoresced more than others. Such a defect, however, showed that the fluorescent salt increased the rapidity of the action upon the photographic film. The result of this experiment, as well as that of others, has sufficiently established the fact that the fluorescent screen is of great importance in connection with the art of rapid sciagraphy.
Phosphor sulphide of zinc is among those which hasten photographic action. (Chas. Henry, in Comptes Rendus, Feb. 10, ’96.) Dr. W. J. Morton employed the screen in taking the sciagraph of the thorax, p. [61]. The advantageous use is also confirmed by Basilewski (Comptes Rendus, March 23, ’96. From trans. by Louis M. Pignolet).—The photographic plate was covered with a sheet of paper coated with barium and platino cyanide, so that the two prepared surfaces were in contact, and the fluorescent paper was between the object and the plate.
Thorax. [§ 206].
By W. J. Morton, M.D. Fluorescent screen used ([§ 151]).
Normal Elbow. [§ 204].
By Prof. Miller.
J. W. Gifford, (Nature, May 21, ’96) tried a great variety of fluorescent bodies in combination with the photographic plate, and found that potassium platino cyanide was decidedly the best.
152. Thompson’s (S. P.) Experiment. Penetrating Power of X-rays Varies with the Vacuum. Comptes Rendus. CXIII., p. 809. The Elect., Lon., April 24, ’96, p. 866. In a communication to the Académie des Sciences Prof. Sylvanus P. Thompson of the University College of Liverpool, argued that by one kind of X-rays the bones of the hand were more easily penetrated than by another kind. The two varieties were produced by different vacua. [§ 75] and [76]. Let the vacuum be supposed to become higher and higher. At the first generation of the X-rays, the fluorescent screen showed that the bones of the hand cast very dark shadows. With increase of the vacuum, the shadows of the bones were very faint. This result is also obtained by reduction of temperature. [§ 152a].