ingle day would be long enough to wind round this earth twenty-seven
times at the equator. It appears that the total production of cotton
yarn each day in all the mills together would be on the average about
one hundred and fifty-five million miles. In fact, if they would only
spin about one-fifth more, we could assert that Great Britain produced
enough cotton yarn every day to stretch from the earth to the sun and
back again! It is not hard to find from these figures how long it
would take for all the mills in Lancashire to produce a piece of yarn
long enough to reach from our earth to the nearest of the stars. If
the spinners worked as hard as ever they could for a year, and if all
the pieces were then tied together, they would extend to only a small
fraction of the distance; nor if they worked for ten years, or for
twenty years, would the task be fully accomplished. Indeed, upwards of
four hundred years would be necessary before enough cotton could be
grown in America and spun in this country to stretch over a distance
so enormous. All the spinning that has ever yet been done in the world
has not formed a long enough thread!

There is another way in which we can form some notion of the immensity
of these sidereal distances. You will recollect that, when we were
speaking of Jupiter's moons, I told you of the beautiful discovery
which their eclipses enabled astronomers to make. It was thus found
that light travels at the enormous speed of about one hundred and
eighty-five thousand miles per second. It moves so quickly that within
a single second a ray would flash two hundred times from London to
Edinburgh and back again.

We said that a meteor travels one hundred times as swiftly as a
rifle-bullet; but even this great speed seems almost nothing when
compared with the speed of light, which is ten thousand times as
great. Suppose some brilliant outbreak of light were to take place in
a distant star--an outbreak which would be of such intensity that the
flash from it would extend far and wide throughout the universe. The
light would start forth on its voyage with terrific speed. Any
neighboring star which was at a distance of less than one hundred and
eighty-five thousand miles would, of course, see the flash within a
second after it had been produced. More distant bodies would receive
the intimation after intervals of time proportioned to their
distances. Thus, if a body were one million miles away, the light
would rea