ABSTRACT
The consequence of such changes is that the radioactive elements and their ultimately inactive products are found in one or other of the last twelve places of the periodic table from thallium to uranium, and though not identical in atomic weight with the long known elements are indistinguishable from them. For it is obvious that these conclusions, if accepted, involve an entirely new view of the nature of the elements and the constitution of matter. It will have been noticed by the reader that the radio-active elements thus far referred to are found among the last few members of the series in the periodic table possessing the highest atomic weights known. The only elements of relatively small atomic weight which have been found to exhibit an appreciable activity, though weak, are potassium and rubidium.
