"A north and south line will run straight across this, at right
angles, and I can draw it pretty accurately with my eye, but to be
exact I have measured this line as you see. Now I'll draw a line as
nearly as I can straight across this one, and of precisely the same
length."

He drew and staked the second line, and this is what he had:

[Illustration]

"Now," he said, "if I have drawn my last line exactly at right angles
with my first one, it runs north and south; and to find out whether or
not I have drawn it exactly, I must measure. If it is just right it
will be precisely the same distance from the south stake to the east
stake as from the south stake to the west stake; and from the east
stake to the south one will be southwest, while from the west to the
south will be south-east."

With that Sam measured, and found that he was just a trifle out.
Readjusting his north and south stakes, he soon had his lines right.

"Now," he resumed, "I know the points of the compass, and I'll explain
how you can help me. Our course lies exactly in a line from me through
that big gum tree over there to the dead sycamore beyond. If we go
toward the gum, keeping it always in a line with the sycamore, we
shall go perfectly straight, of course; and by choosing another tree
away beyond the sycamore and in line with it, just before we get to
the gum tree, we shall still go on in a perfectly straight line. We
might keep that up for any distance, and travel in as straight a line