The plate was wrapped in two thicknesses of black paper. The objects were placed upon this and the radio-active ore, separated by a board one inch thick, was placed above. The exposure lasted five days. The action is much less rapid and the result not so clearly defined as in the case of photographs taken by X rays. Of course, the removal of the board and the use of more concentrated preparations of radium would give quicker and better results. The method, however, on account of time consumed and lack of definition is ill adapted to accurate work.
Discharge of Electrified Bodies
The radiations from radio-active bodies can discharge both positively and negatively electrified bodies by making the air surrounding them a conductor of electricity. To demonstrate this, use is made of an electroscope. If the hinged leaf of such an instrument be electrically charged and a radio-active body be brought into its neighborhood, the electricity will be discharged and the leaf return to its original position. The rapidity of this discharge is used to measure the degree of activity of the body giving off the radiation.
Fig. 3—Photograph of Various Objects taken by means of Pitchblende
Fig. 4.—Gold-leaf Electroscope.
The gold-leaf L is attached to a flat rod R and is insulated inside the vessel by a piece of amber S supported from the rod P. The system is charged by a bent rod CC' passing through an ebonite stopper. After charging, it is removed from contact with the gold-leaf system. The rods P and C and the cylinder are then connected with the earth.
Scintillations on Phosphorescent Bodies