They started once more along the edge of the black belt.  The forester was walking well within the burned area.  The two boys centred their attention on the strip between the forester’s tracks and the edge of the black area.  This was a strip roughly fifty to seventy-five feet wide.  Practically everything was blackened in this area.  A piece of unburned paper would have shown with startling distinctness.  But there were no pieces to show.  The forester crossed the black belt from brook to mountain, and the boys kept pace with him for a little.  Then Lew turned back in order to listen in, while Charley went on with the forester.  For a long time the two searched among the leaves, but found nothing to indicate where or how the fire had started.

“The fact that we can’t find where it started,” said the forester at last, “is what makes me suspicious.  A fire can generally be traced.  I guess we’ll have to give up.  I’ll get back to headquarters, and you go home and make your arrangements as quickly as possible.  Then report to me.”

“We’ll go right back with you,” said Charley.  “That is, we will if Lew is willing.  It would hardly be right to ask him to give up his fishing trip.  And, anyway, two of us could guard the forest better than one.”

“That’s true, but until you are regularly sworn in you will not have the legal authority you should have as a fire patrol.”

“Then if Lew is willing, we’ll go right out with you.  We can take the train at Oakdale.”

They returned to Lew and explained the situation.  “Of course we’ll go home,” protested Lew.  “This is your chance, Charley.  You don’t think I’d stand in your way, do you?”

“Thanks, Lew,” said Charley, holding out his hand to his chum.  “But I hate to cut your trip short.”

“That’s easily fixed,” said the forester.  “Go home and make your arrangements and bring Lew back with you for the rest of the vacation if he wants to come.  You can do your patrol work and still catch some fish.  And I’d feel a lot easier to know two of you were here.  You’ve proved that you are good fire fighters.”

Charley called up Willie and told him they were about to leave the forest and would be in Oakdale in about four hours.  Then the wireless was quickly dismantled and packed, and the little party started across the burned area once more, on their way out to the distant road.

They did not forget to examine the ground as they went.  They had gone perhaps a hundred feet when Charley noticed a heap of burned leaves.  They were in the cut-over area, and the floor of the forest had apparently been carpeted thinly and evenly with leaves.  So the little mound caught his eye.  At first he thought nothing of it.  But when his glance swept the surrounding ground and he saw how very thin the ashy coating was, and what a dense pile of ashes was in this little heap, he wondered why the leaves should have collected in this way.  Without