vably large to the inconceivably
small. Our sun is, as far as our present knowledge goes, one of modest
dimensions. Arcturus and Canopus must be thousands of times larger than
it. Yet our sun is 320,000 times heavier than the earth, and the earth
weighs some 6,000,000,000,000,000,000,000 tons. But it is only in
resolving these stupendous masses into their tiniest elements that we
can reach the ultimate realities, or foundations, of the whole.

Modern science rediscovered the atoms of Democritus, analysed the
universe into innumerable swarms of these tiny particles, and then
showed how the infinite variety of things could be built up by their
combinations. For this it was necessary to suppose that the atoms were
not all alike, but belonged to a large number of different classes. From
twenty-six letters of the alphabet we could make millions of different
words. From forty or fifty different "elements" the chemist could
construct the most varied objects in nature, from the frame of a man to
a landscape. But improved methods of research led to the discovery
of new elements, and at last the chemist found that he had seventy or
eighty of these "ultimate realities," each having its own very definite
and very different characters. As it is the experience of science to
find unity underlying variety, this was profoundly unsatisfactory, and
the search began for the great unity which underlay the atoms of matter.
The difficulty of the search may be illustrated by a few figures. Very
delicate methods were invented for calculating the size of the atoms.
Laymen are apt to smile--it is a very foolish smile--at these figures,
but it is enough to say that the independent and even more delicate
methods suggested by recent progress in physics have quite confirmed
them.

Take a cubic millimetre of hydrogen. As a millimetre is less than 1/25th
of an inch, the reader must imagine a tiny bubble of gas that would fit
comfortably inside the letter "o" as it is printed here. The various
refined methods of the modern physicist show that there are 40,000
billion molecules (each consisting of two atoms of the gas) in this tiny
bubble. It is a little universe, repeating on an infinitesimal scale the
numbers and energies of the stellar universe. These molecules are not
packed together, moreover, but are separated from each other by spaces
which are enormous in proportion to the size of the atoms. Through these
empty spaces the atoms dash at an averag