Röntgen rays : memoirs by Röntgen, Stokes, and J. J. Thomson / translated and edited by George F. Barker.

  • Röntgen, Wilhelm Conrad, 1845-1923.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Röntgen rays : memoirs by Röntgen, Stokes, and J. J. Thomson / translated and edited by George F. Barker. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

    16/92 (page 6)
    Thickness Relative Thickness Density Pt 0.018 mm. 1 21.5 Pb 0.05 3 11.3 Zn 0.10 6 7.1 Al 3.5 200 2.6 We may conclude from these values that different metals possess transparencies which are by no means equal, even when the product of thickness and density are the same. The trans- parency increases much more rapidly than this product de- creases. 6. The fluorescence of barium platino - cyanide is not the only recognizable effect of the X-rays. It should be mentioned that other bodies also fluoresce; such, for instance, as the phos- phorescent calcium compounds, then uranium glass, ordinary glass, calcite, rock-salt, and so on. Of special significance in many respects is the fact that photographic dry plates are sensitive to the X-rays. We are, therefore, in a condition to determine more definitely many phenomena, and so the more easily to avoid deception; wher- ever it has been possible, therefore, I have controlled, by means of photography, every important observation which I have made with the eye by means of the fluorescent screen. In these experiments the property of the rays to pass almost unhindered through thin sheets of wood, paper, and tin-foil is most important. The photographic impressions can be ob- tained in a non-darkened room with the photographic plates either in the holders or wrapped up in paper. On the other hand, from this property it results as a consequence that un- developed plates cannot be left for a long time in the neighbor- hood of the discharge-tube, if they are protected merely by the usual covering of pasteboard and paper. It appears questionable, however, whether the chemical ac- tion on the silver salts of the photographic plates is directly caused by the X-rays. It is possible that this action proceeds from the fluorescent light which, as noted above, is produced