orm molecules. Atoms and molecules are the bricks out of which
nature has built up everything; ourselves, the earth, the stars, the
whole universe.

But more than bricks are required to build a house. There are other
fundamental existences, such as the various forms of energy, which give
rise to several complex problems. And we have also to remember, that
there are more than eighty distinct elements, each with its own definite
type of atom. We shall deal with energy later. Meanwhile it remains to
be said that, although we have discovered a great deal about the
electron and the constitution of matter, and that while the physicists
of our own day seem to see a possibility of explaining positive and
negative electricity, the nature of them both is unknown. There exists
the theory that the particles of positive and negative electricity,
which make up the atoms of matter, are points or centres of disturbances
of some kind in a universal ether, and that all the various forms of
energy are, in some fundamental way, aspects of the same primary entity
which constitutes matter itself.

But the discovery of the property of radio-activity has raised many
other interesting questions, besides that which we have just dealt with.
In radio-active elements, such as uranium for example, the element is
breaking down; in what we call radio-activity we have a manifestation of
the spontaneous change of elements. What is really taking place is a
transmutation of one element into another, from a heavier to a lighter.
The element uranium spontaneously becomes radium, and radium passes
through a number of other stages until it, in turn, becomes lead. Each
descending element is of lighter atomic weight than its predecessor. The
changing process, of course, is a very slow one. It may be that all
matter is radio-active, or can be made so. This raises the question
whether all the matter in the universe may not undergo disintegration.

There is, however, another side of the question, which the discovery of
radio-activity has brought to light, and which has effected a revolution
in our views. We have seen that in radio-active substances the elements
are breaking down. Is there a process of building up at work? If the
more complicated atoms are breaking down into simpler forms, may there
not be a converse process--a building up from simpler elements to more
complicated elements? It is probably the case that both processes are at
work.

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