Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 edition. Excerpt: ... CHAPTER XIII. THE "ROENTGEN" RAYS AND RADIOGRAPHY. Although the remarkable discovery that it was possible by electrical means to depict an image of an object on a photographic sensitized plate, despite the intervention of solid bodies, was fiist given to the world at large by Professor Roentgen, yet he was undoubtedly led to the results by consideration of the works of previous experimenters in electrical discharges through vacua. It is not intended here to trace the previous work of Professor Crookes, the inventor of the radiometer, which is actuated by the heat rays of light, nor of Hertz, who found that gold leaf was transparent to rays emanating from certain vacuum tubes carrying a luminous electrical discharge. Nor can we stop to investigate the experiments of Philip Lenard, who replaced a portion of the tube by an aluminium window, and yet obtained fluorescence from the rays passing through this window. Professor Crookes claimed to have discovered a fourth state of matter--viz., "radiant matter," the previous three states being, as every student knows, gaseous, liquid, and solid. This he inferred from the effects obtained by the passage of hightension currents through glass tubes which he exhausted of air to a far greater degree of attenuation than previously attained. Certain ones of these tubes have been mentioned in a previous chapter and illustrated in Figs. 31, 33, and 34. But these earlier experimenters attributed their results to the action of the simple cathode rays (rays emanating from the tube terminal termed the cathode from its connection to the negative pole of the generator). They had not as yet become cognizant of certain rays now known as Roentgen or X rays, which were to be found also at the cathode. In a previous...
