These chemical properties have not yet been perfectly defined; thus M.
Debierne, who discovered actinium, has been able to note the active property which seems to belong to it, sometimes in lanthanum, sometimes in neodynium.[33] It is proved that all extremely radioactive bodies are the seat of incessant transformations, and even now we cannot state the conditions under which they present themselves in a strictly determined form.
[Footnote 33: Polonium has now been shown to be no new element, but one of the transformation products of radium.

Radium itself is also thought to be derived in some manner, not yet ascertained, from uranium.

The same is the case with actinium, which is said to come in the long run from uranium, but not so directly as does radium.

All this is described in Professor Rutherford's _Radioactive Transformations_ (London, 1906) .-- ED.] Sec.3.THE RADIATION OF THE RADIOACTIVE BODIES AND THE EMANATION To acquire exact notions as to the nature of the rays emitted by the radioactive bodies, it was necessary to try to cause magnetic or electric forces to act on them so as to see whether they behaved in the same way as light and the X rays, or whether like the cathode rays they were deviated by a magnetic field.

This work was effected by Professor Giesel, then by M.Becquerel, Professor Rutherford, and by many other experimenters after them.