The outlines of physics: an elementary text-book . rials, .such as glass. They affect the photographicfilm, so that shadow photographs inay be taken them; and they render certain substances, such as cal-cium tungstate, zinc oxide, and many of the double plati-num cyanides, luniinous. If a screen coated with one ofthese substances be placed in the path of the X rays, theshadow of any body interposed will be visible upon thescreen. This will be the shadow of those portions of thebody which are opaque to the X rays, and not of thoseopaque to oirdinary light. Thus, if the arm be interpo
The outlines of physics: an elementary text-book . rials, .such as glass. They affect the photographicfilm, so that shadow photographs inay be taken them; and they render certain substances, such as cal-cium tungstate, zinc oxide, and many of the double plati-num cyanides, luniinous. If a screen coated with one ofthese substances be placed in the path of the X rays, theshadow of any body interposed will be visible upon thescreen. This will be the shadow of those portions of thebody which are opaque to the X rays, and not of thoseopaque to oirdinary light. Thus, if the arm be interposed,the two bones will be clearly visible, but the fleshy partof the arm will scarcely cast any shadow. Photographs taken with the X rays possess the samepeculiarity. Figure 226 is a reproduction of such a photo- ^ From Dr. Geissler, of Bonn. THE ELECTRIC SPARK 268 It shows the bones of the human wrist; also abit of broken needle which had become lodged in themembrane surrounding one of the bones. The outline ofthe wrist is dimly Fig. From a photograph taken by R. W. Quick. 264 THE OUTLINES OF PHYSICS CHAPTER XXVI THE ELECTRIC CURRENT SijH ?^ +
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectphysics
