"Giesel also has obtained from pitchblende a radio-active substance which in many respects is similar to the actinium of Debierne. The active substance belongs to the group of cerium earths, and is precipitated with them. The method of preparation of this material is the same as that employed for the separation of the rare earths. This substance is similar in radio-active behavior to thorium, but intensely active in comparison. From the method of separation, thorium itself cannot be present except in minute quantity. ...If a piece of paper is placed in a small closed vessel containing the active material, in a short time the paper itself becomes powerfully active. This is especially the case if it is moistened with water."