oactive
substances, the quality of the secondary radiation emitted by the
different elements, are all determined by the atomic weight of the
element."[1]

[Footnote 1: Encyclopaedia Britannica, Vol. XVII, 891. Cambridge
Edition.]

Just recently we have had opened up before us a still more intimate
inner-circle view of the composition of matter. H.G.J. Moseley, a young
man only twenty-six years of age, at an English university, devised a
method of examining the spectra of the various elements by means of the
X-rays. He found in this way that the principal lines of these various
spectra are connected by a remarkably simple arithmetical relationship;
for when the elements are arranged in the order of their atomic weights,
they show a graded advance from one to another equal to successive
additions of the same electrical unit charge, thus indicating a real
gamut of the elements that we can run up by adding or run down by
subtracting the same unit of electrical charge. It is pitiable to have
to record that next year this scientific genius was killed in the
ill-fated Gallipoli expedition against Turkey.

Thus in many fairly independent ways we are brought around to this same
idea of a common structure underlying all the many seeming diversities
manifested by what we call matter.

The phenomena of radioactivity were discovered accidentally in 1896 by
the French chemist Becquerel. Many investigators immediately began
working along this promising line, and two years later Madam Curie, in
association with others, discovered the new element radium. Soon it was
discovered that radium and several other substances are continually
giving off radiations at an enormous rate, that no change of chemical
combination, no physical change of condition appears to have the
slightest effect in slowing or increasing this discharge of emanations,
while no scientific apparatus yet devised can detect any change in the
substances left behind either in respect to weight or any other
properties as the result of these enormous losses of energy. Accordingly
some people not unnaturally were ready to draw the conclusion that those
most firmly established laws of physics and chemistry, the laws of the
conservation of energy and of matter, were overthrown by this
astonishing behavior of these newly discovered substances. However, only
a few more years of study and investigation were necessary to prove
that this last conclusion was wholly unwarranted; an