Make a fold in the paper, as shown by the dotted line in the
illustration. Then, taking any two points, as A and B, describe
semicircles on the line alternately from the centres B and A, being
careful to make the ends join, and the thing is done. Of course this is
not a _true_ spiral, but the puzzle was to produce the _particular_
spiral that was shown, and that was drawn in this simple manner.
[Illustration]