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.
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; and to-day these laws of the conservation of energy and
of matter are more firmly established than ever.
The thing that has gone by the board is the old idea of the atoms as the
indivisible and irreducible minima of the material universe. For not
only do all the radioactive substances give off particles of helium gas
positively electrified, but _all bodies, no matter what their
composition_, can by suitable treatment, such as exposing them to
ultra-violet light, or raising them to incandescence, be made to give off
electrons or negatively charged particles, and these electrons are
always the same no matter from what kind of substance they come. In a
somewhat similar way, we always get positively electrified particles of
the mass of the hydrogen atom, or about 1,760 times the mass of the
electron, whenever we send an electric charge through a gas at very low
pressure, no matter what the kind of gas. Whether or not these positive
units will yet prove susceptible of being split up into smaller particles
comparable to the electrons, is merely a subject for conjecture. We
have no proof that they will. At the present time what we call matter
seems to be composed of these positive units and of the electrons which
are about 1/1760 as great; and in the present state of our knowledge
these facts suffice to explain all the properties of matter. Thus we can
either say that electricity is composed of matter, or say that matter is
composed of electricity; and human language at best is such a clumsy
vehicle of thought that scientifically and philosophically the one
statement is as correct and as reasonable as the other.
And probably we shall never be able to learn any more than this. We
have arrived at a sort of box-within-a-box theory of the make-up of
matter. By a very elaborate system of unpacking, or by some
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