ABSTRACT
The changes in radium are not completed at the stage, for it will be shown that there is very strong evidence that there are at least two more slow transformations. Active has been subjected. The inside of a long glass tube was covered with equal areas of thin metal, including aluminium, iron, and copper, silver, lead and platinum. A large amount of radium emanation was introduced into the tube, and tube closed. After seven days the metal plates were removed, and, after allowing two days to elapse for the ordinary excited activity to disappear, the residual activity of the plates was tested by an electrometer. The initial irregularities in the decay curves of the different metals are, in all probability, due to slight but different degrees of absorption of the radium emanation by the metal plates, the absorption being greatest for copper and silver and least for aluminium. The variation of the residual activity with time will first be considered.
