first disappeared. The supposition is that the helium is the product of the atomic decomposition of the radioactive gas. It may be argued that the experiments only prove that radium is not an element, but only a compound of staple elements. On the other hand, the production of this radioactive gas is not influenced by changes of temperature, which is true of no chemical process, and is accompanied by radioactivity, which is not a phenomenon of chemical changes.
The wide distribution of radioactive matter has been brought to light by the work of Professors Elster and Geitel in Germany on the radioactivity of the atmosphere and soils, and by a number of observers under the leadership of Professor J. J. Thomson on the presence of a radioactive gas in many spring and well waters. Elster and Geitel discovered that clay is much more active than other soils, apparently from the presence of a trace of radium, though much depends on the locality. A certain clay which they
examined contained one eleven-hundredth as much radium as pitchblende, the ore from which radium is extracted. Radium salts are found to give off heat at a very considerable rate. M. Curie estimates that radium can melt its weight of ice in an hour. A more exact investigation by Rutherford and Barnes shows that the radioactive gas and the secondary activity are the chief sources of the heating effect.
The treatment of certain diseases, particularly of cancer and lupus, by means of radium radiation continues to attract much attention from physicians both in this country and in Europe. A committee appointed by the Vienna Academy of Science to investigate the results of the treatment of cancer with radium reported that in nine cases in which the treatment was used abatement in the cancerous swelling resulted and in two of these cases the swelling had not reappeared after five months' time. A case of cancer of the palate was much improved by the treatment. The use of radium is
