says that the physical as well as the chemical properties of the various
elements depend upon their atomic weights, or as it is stated in the
language of mathematics, the properties of an element are functions of
its atomic weight. This fact of the variation in the properties of
elements in accord with their atomic weights has been even more
strikingly illustrated by the behavior of discharges of electricity
through rarified gases, as well as by the facts of radioactivity. To
quote the words of Sir J.J. Thompson, "The transparency of bodies to
Roentgen rays, to cathode rays, to the rays emitted by radioactive
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: Encyclopædia 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.