six
million miles. Imagine that on Midsummer Day, when standing on the
earth here, I measure with a piece of card the angle between the star
and the sun. Six months later, on Midwinter Day, when the earth is at
the opposite point of its orbit, I again measure the angle between the
same star and the sun, and we can now determine the star's distance by
making a triangle. I draw a line a foot long, and we will take this
foot to represent one hundred and eighty-six million miles, the
distance between the two stations; then placing the cards at the
corners, I rule the two sides and complete the triangle, and the star
must be at the remaining corner; then I measure the sides of the
triangle, and how many feet they contain, and recollecting that each
foot corresponds to one hundred and eighty-six million miles, we
discover the distance of the star. If the stars were comparatively
near us, the process would be a very simple one; but, unfortunately,
the stars are so extremely far off that this triangle, even with a
base of only one foot, must have its sides many miles long. Indeed,
astronomers will tell you that there is no more delicate or
troublesome work in the whole of their science than that of
discovering the distance of a star.

In all such measurements we take the distance from the earth to the
sun as a conveniently long measuring-rod, whereby to express the
results. The nearest stars are still hundreds of thousands of times as
far off as the sun. Let us ponder for a little on the vastness of
these distances. We shall first express them in miles. Taking the
sun's distance to be ninety-three million miles, then the distance of
the nearest fixed star is about twenty millions of millions of
miles--that is to say, we express this by putting down a 2 first, and
then writing thirteen ciphers after it. It is, no doubt, easy to speak
of such figures, but it is a very different matter when we endeavor to
imagine the awful magnitude which such a number indicates. I must try
to give some illustrations which will enable you to form a notion of
it. At first I was going to ask you to try and count this number, but
when I found it would require at least three hundred thousand years,
counting day and night without stopping, before the task was over, it
became necessary to adopt some other method.

When on a visit in Lancashire I was once kindly permitted to visit a
cotton mill, and I learned that the cotton yarn there produced in a
s