er of molecules and atoms. How many molecules there are
in a cubic inch of air under ordinary pressure has been determined, and
is represented approximately by a huge number, something like a thousand
million million millions.

When the diameter of a molecule has been measured, as it has been
approximately, and found to be about one fifty-millionth of an inch,
then fifty million in a row would reach an inch, and the cube of fifty
million is 125,000,000000,000000,000000, one hundred and twenty-five
thousand million million millions. In a cubic foot there will of course
be 1728 times that number. One may if one likes find how many there may
be in the earth, and moon, sun and planets, for the dimensions of them
are all very well known. Only the multiplication table need be used, and
the sum of all these will give how many molecules there are in the solar
system. If one should feel that the number thus obtained was not very
accurate, he might reflect that if there were ten times as many it would
add but another cipher to a long line of similar ones and would not
materially modify it. The point is that there is a definite, computable
number. If one will then add to these the number of molecules in the
more distant stars and nebulae, of which there are visible about
100,000,000, making such estimate of their individual size as he thinks
prudent, the sum of all will give the number of molecules in the visible
universe. The number is not so large but it can be written down in a
minute or two. Those who have been to the pains to do the sum say it may
be represented by seven followed by ninety-one ciphers. One could easily
compute how many molecules so large a space would contain if it were
full and as closely packed as they are in a drop of water, but there
would be a finite and not an infinite number, and therefore there is a
limited number of atoms in the visible universe.

THE ETHER IS UNLIMITED.

The evidence for this comes to us from the phenomena of light.
Experimentally, ether waves of all lengths are found to have a velocity
of 186,000 miles in a second. It takes about eight minutes to reach us
from the sun, four hours from Neptune the most distant planet, and from
the nearest fixed star about three and a half years. Astronomers tell us
that some visible stars are so distant that their light requires not
less than ten thousand years and probably more to reach us, though
travelling at the enormous rate of 186,000 mile