"Debierne has obtained from pitchblende a very active substance which he named actinium. This active substance is precipitated with the iron group, and appears to be very closely allied in chemical properties to thorium, though it is many thousand times more active. It is very difficult to separate from thorium and the rare earths. ...Debierne has obtained a substance comparable in activity with radium. The separation, which is difficult and laborious, has so far not been carried far enough to bring out any new lines in the spectrum. Actinium gives out easily absorbed and penetrating deviable rays like those of radium, and also a radio-active emanation, which is more allied to the emanation of thorium than to that of radium. The emanation has a distinctive rate of decay; it loses its activity in the course of a few seconds, while the thorium emanation loses half its activity in one minute. The distinctive character of the radiations and emanations, together with the permanence of the activity; make it very probable that actinium will prove to be a new element of very great activity."