"Yes, but Sam," said Tom, suddenly thinking of something.

"Well, what is it, Tom?"

"Suppose you guess wrong as to the distance travelled each day?"

"Well, suppose I do; I can't miss it very far."

"No, but it gives you a wrong starting-point for the next day, and two
or three mistakes would throw you clear out."

"Yes, but I make corrections constantly. You see, I have changed the
place of last night's camp a little on the map."

"How do you make corrections?"

"By the creeks and rivers. Here, for instance, is a creek that we
ought to cross about ten miles ahead. If we come to it short of that,
or if it proves to be further off, I shall know that I have got
to-night's camp placed wrong on the map. I shall then correct my
estimate. When we come to the next creek I shall be able to make my
guess still more certain, and by the time we get to Pensacola I shall
have the whole march marked pretty nearly right on the map."

"I'd give a purty price for that there head o' your'n, Sam," said Sid
Russell.

"It isn't for sale, Sid, and besides it will be a good deal cheaper to
use the one you have, taking care to make it as good as anybody's. Now
let me explain to all of you why we are going to Pensacola," and with