difficult for anyone to attempt to solve it, but
at last an ingenious method was devised, a method which shows once more
the triumph of man's mind over difficulties. In practice this method is
extremely difficult to carry out, for it is complicated by so many other
things which must be made allowance for; but in theory, roughly
explained, it is not too hard for anyone to grasp. The way of it is
this: If you hold up your finger so as to cover exactly some object a
few feet distant from you, and shut first one eye and then the other,
you will find that the finger has apparently shifted very considerably
against the background. The finger has not really moved, but as seen
from one eye or the other, it is thrown on a different part of the
background, and so appears to jump; then if you draw two imaginary
lines, one from each eye to the finger, and another between the two
eyes, you will have made a triangle. Now, all of you who have done a
little Euclid know that if you can ascertain the length of one side of a
triangle, and the angles at each end of it, you can form the rest of the
triangle; that is to say, you can tell the length of the other two
sides. In this instance the base line, as it is called--that is to say
the line lying between the two eyes--can easily be measured, and the
angles at each end can be found by an instrument called a sextant, so
that by simple calculation anyone could find out what distance the
finger was from the eye. Now, some ingenious man decided to apply this
method to the stars. He knew that it is only objects quite near to us
that will appear to shift with so small a base line as that between the
eyes, and that the further away anything is the longer must the base
line be before it makes any difference. But this clever man thought that
if he could only get a base line long enough he could easily compute the
distance of the stars from the amount that they appeared to shift
against their background. He knew that the longest base line he could
get on earth would be about eight thousand miles, as that is the
diameter of the earth from one side to the other; so he carefully
observed a star from one end of this immense base line and then from the
other, quite confident that this plan would answer. But what happened?
After careful observations he discovered that no star moved at all with
this base line, and that it must be ever so much longer in order to make
any impression. Then indeed the case seem