magic of fluroscent writting...............

If a design be written or drawn on white paper, using a solution of sulphate of quinine as the ink, such design or writing when dry will be quite invisible. But if it be exposed in a dark room to the light of an ordinary Geissler tube or similar electric light the writing or design will appear in blue.

Similarly, if tungstate of calcium were used on a" brownish TIG. 8. or darkish paper, and the design exposed to the action of the X Rays (the X Ray bulb could itself be wrapped in black paper or placed in a cardboard or even a wooden box), it would appear in phosphorescent white.

If the (much dearer) chemical, barium platinocyanide be used, tne phosphorescence is much stronger and of a greenish tinge. It is with this chemical that X Ray
screens are. coated. Another chemical almost equally brilliant (phosphorescing blue) is potassium platinocyanide; it is also equally dear.