"That's so; but how's the old sycamore to help us?"

"By giving us a point to take sight from. Let me show you. Our proper
course of march is in the direction of a line drawn from the sycamore
to this pine tree. What we want to do is to prolong that line, and
find some tree further on that stands in it. If I stand on the line,
between the sycamore and the pine and turn my face toward the pine,
I'll be looking in exactly the right direction, and can pick out the
right tree to march to, by sighting on the pine. The trouble is to get
in the right place to take sight from. To do that I must find the line
between the sycamore and the pine. Now you go over there beyond the
pine, and take sight on it at the sycamore till you get the two trees
in a line with you. Then I'll stand over here, between the two object
trees, and move to the right or left as you tell me to do, till you
find that I am exactly in the line between them. Then I can pick out
the right tree ahead."

Sid did as he was told, the boys all looking on with great interest,
and presently Sam had selected their next object tree. The boys were
astonished greatly at what they thought Sam's marvellous knowledge,
but to their wondering comments Sam replied:--

"I haven't done anything wonderful. A little knowledge of mathematics
has helped me, perhaps, but there isn't a thing in all this that isn't
perfectly simple. Any one of you might have found out all this for
himself, without books and without a teacher. It only requires you to
think a little and to use your eyes. Besides you've all done the same
thing many a time."

"I'll _bet_ I never did," said Billy Bowlegs.