coiling it neatly. "We came out here just for the purpose, boys!"

"You did?" inquired Jack. "Why, how'd you know we were here?"

"Oh," went on Jimmie with a lofty air, "everybody pretty near knows
you're here. Next time you'd better be careful and shut the dampers
when you make a fire. That smoke was a dead give-away!"

"Ah, ha, smarty!" declared Jack. "That's where you're wrong. We
didn't make any smoke at all. So that punctures your balloon."

"Well, anyhow," went on Jimmie unabashed, "a little bird told us."

"Now, see here, Jimmie," put in Ned as the five boys started for the
camp near the Eagle, "tell me the exact truth. It may have serious
consequences if you don't. Does anyone know we are here?"

"Not that I know of, Ned," was Jimmie's sober reply. "We just stumbled
onto you as you were tracking something in the woods."

"Oh, that reminds me," Ned said, halting. "We were on the track of
some fellow who visited our position and took out the spark plugs from
our engines. We were following his tracks in the woods when you came."

"What sort of a guy was he?" asked Jimmie, intensely interested.

"I don't know," answered Ned. "We haven't seen him yet."

"Didn't he leave any signs at all?" went on Jimmie. "Did he come and
go in an airship, or did he have wings and fly through the air?"

"Neither," declared Ned. "He left some pretty fair tracks."

"Then we'll get him!" asserted Jimmie, positively. "He can't get away.
Once we get on his trail he might as well quit!"

"Good boy, Jimmie!" laughed Ned. "You're a sight for sore eyes. And,"
he went on, "it's a pleasure to have your optimism to help."

"Thanks!" drily responded the Wolf. "Where are his tracks?"

"Right around here at the front of the machine near the engine."

"See anything, Dave?" asked Jimmie, at once, as the boys grouped about
the Eagle, being careful not to tread in the tracks left by the one who
had meddled with their engines.

"Yes," responded Dave, instantly. "He was a shortish chap, you know,
because he had to stand on his toes here to reach the engines."

"And I think he was a Uhlan," went on Jimmie, pointing to other tracks.
"I can see the mark of the spur chain under his instep."

"He must have put his hand right here," added Dave, indicating a spot
on the forward wings that showed grimy finger marks. "He had a scar
extending across all four fingers. See the print on it?"

"I'll bet I know who it was!" dec