Herr
Gruhn has by patient labour, and experiment arrived at the conclusion
that " all bodies give out emanations, each of them possessing an
emanation of its own." Dr. Gustave Le Bon has detected an ionising
emanation in all metals, it having been suggested two years previously
by Professor Thomson that every substance possesses a characteristic
radiation in proportion to its density. Herr Gruhn notices the motive
forces in metallic rods, as affected by the weather. And it has been
shown by Professor Rutherford that emanations supposed to belong
naturally to substances other than the acknowledged radio-active
substances, radium, thorium, actinium, and polonium, have been gained
by these substances through exposure to the atmosphere, which always
contains a certain amount of radium. " It seems reasonable therefore to
suppose, " says a leading scientist of to-day, " that Herr Gruhn has
done much towards proving the existence of a new force, one, moreover,
which is specially exercised in the case of this, or that metal." "
Although at present there may be no positive means of detecting the
characteristic radiations thus referred to, it is not at all improbable
that the day is at hand when apparatus will be devised of sufficient
delicacy, and of such a type as to detect them." " When this shall be
done, the problem, moreover, of the ' divining-rod ' will be solved,
since the familiar electroscope has been the ' divining-rod ' of
radio-activity." Lord Kelvin said as long ago as in 1892, that " for
the happy individual whose destiny it is to conclusively unravel the
hitherto bewildering enigma of the divining rod, his reward will be the
honour of fixing an added laurel on the crown of applied science
