ctivity, which is about a hundred thousand times greater than that of
uranium.

Radium produces various chemical and some very intense physiological
reactions. Its salts are luminous in the dark, but this luminosity, at
first very bright, gradually diminishes as the salts get older. We
have here to do with a secondary reaction correlative to the
production of the emanation, after which radium undergoes the
transformations which will be studied later on.

The method of analysis founded by M. and Madame Curie has enabled
other bodies presenting sensible radioactivity to be discovered. The
alkaline metals appear to possess this property in a slight degree.
Recently fallen snow and mineral waters manifest marked action. The
phenomenon may often be due, however, to a radioactivity induced by
radiations already existing in the atmosphere. But this radioactivity
hardly attains the ten-thousandth part of that presented by uranium,
or the ten-millionth of that appertaining to radium.

Two other bodies, polonium and actinium, the one characterised by the
special nature of the radiations it emits and the other by a
particular spectrum, seem likewise to exist in pitchblende. 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