to see what sort of a job we're up against. Your motor is pulling hard on the rope, and the moment we take the rope from the tree it will be jerked out of our hands. Don't you know how to run a gas-engine?"

"I know how to start a gas-engine," was the amazing response, "but I don't know how to stop it."

"Py shiminy grickets!" whooped Carl, "you vas a nice pair to shtart off mit a gasolene-air-ship. You vas in luck nod to make some landings on Chupiter, Mars or to hit a comic."

Matt likewise thought it was an odd situation, but believed it would be well to get the two helpless aeronauts down on terra firma before asking for an explanation of their predicament.

"Do either of you know what the gasolene-tank is?" he asked.

The heads disappeared within the car for a moment, then one reappeared over the railing.

"Yes, we've found that, all right," said the man.

"And the carburettor—do you know where to look for that?"

"Is that the thing that makes the spark?"

Carl let off a howl of derision.

"Ach, du lieber, vat a ignorance! Der carpuretter makes der gas, dot makes der exblosions in der cylinter, dot moofs der biston dot makes der bropellor go 'roundt. I know dot meinseluf, efen dough I vasn't so pright like Modor Matt."

"There's a pipe leading from the gasolene-tank to the carburettor," continued Matt, "and there's a valve which should be worked by a lever. Close that valve and you'll shut off the supply of gasolene. When you do that, the motor will stop, and we can work down here to better advantage."

The head disappeared again and the car rocked and swayed as the two men scrambled around in it. Their ignorance, however, increased rather than lessened the difficulty. The misfiring of the one cylinder ceased and the motor took up its humming rhythm at an even faster speed. The fresh impetus of the propeller put a harder pull on the rope, and the strain bore sudden and unexpected results.

With a yell of dismay the driver of the machine leaned over the rail of the car. He had thrown off his hat and his coat was unbuttoned.

"We're making it worse!" he cried. "I wish to thunder you could come up here and——"

Just then the drag-rope, which could not have been properly fastened to the car, let go and dropped earthward in sinuous coils.

The man doubled farther over the rail in a futile and foolish effort to lay hold of it. Something fell from the pocket of his coat, fluttered through the air and landed in the top of a tree.

Matt noted the flight of the fallen object only incidentally, for the major part of his attention was taken up with the actions of the car.

The steering rudder had become elevated, and the air-ship started at a tremendous clip toward the clouds. The two aeronauts could be seen rushing around the car like mad. While the two boys watched, the rudder was brought down to a level; but something else had gone wrong, for the machine could not be maneuvered.

Swiftly the air-ship diminished to a mere speck in the southern sky, and then vanished altogether.

Carl turned a blank look at Matt and gave a long whistle.

"Dot proofs, Matt," said he, "dot id don'd vas goot pitzness to monkey mit t'ings you don'd know nodding aboudt. Oof dose fellers run into a shooding shdar dere vill be some fine smash oops."

"Why they ever ventured up in the air-ship, knowing so little about how to manage it, is a mystery."

Matt gave his head an ominous shake.

"Vat vill pecome oof dem?" queried Carl.

"If they can get the steering rudder to working, they can drive the air-ship to the ground. Anyhow, the supply of gasolene will have to give out, in time, and then they may be able to come down."

"Dere iss somet'ing crooked aboudt dose fellers. Oddervise, dey vouldn't be vere dey are."

"Did you see something drop from the driver's pocket, Carl?"

"Nix. Iss dot vat habbened?"

"Yes. It landed in the top of that tree, over there."

"Meppy ve ged holt oof der t'ing und find oudt somet'ing aboudt who dose fellers vas, und for vy dey vent off for a fly mitoudt knowing how to manach der flyer?"

Matt proceeded to the foot of the tree in whose branches the fallen object had alighted. Lifting his gaze upward, he peered sharply into the foliage.

"I see it," he announced, pointing.

"Und me, too," said Carl. "It vas vite, und round, like a punch oof bapers rolled oop. How ve ged him down, hey? Meppy ve t'row some shticks ad him?"

Suiting his action to the word, Carl picked up clubs and stones and hurled them upward in an endeavor to dislodge the object. Finding that these efforts were unsuccessful, Matt threw off his coat and hat and climbed the tree.

The roll of papers was lodged far out in the fork of a branch. Standing on the branch, he jumped up and down on it and jarred the roll loose. Carl caught it deftly as it fell.

"Hoop-a-la!" he yelled; "here she vas, Matt. Come down a leedle vile ve look him ofer."

In a few moments Matt was again on the ground. The roll, which Carl immediately handed to him, he found to contain a number of sheets wrapped compactly in a piece of white paper.

"I guess we'll open it and not stand on any ceremony," said Matt.

"Sure!" exclaimed Carl. "For vy nod?"

"It's not exactly the right thing to do. They're not our papers and we haven't any business tampering with documents that belong to some one else. Under the circumstances, though, and considering that the whole affair of the air-ship is a strange one, and that we may be able to help the two men in some way through the information the roll may contain, we'll have a look at it."

Going back to the place where they had eaten their lunch, the boys sat down and Matt opened the little bundle. A dozen blue prints of mechanical tracings were revealed. In the center of the roll was a sealed envelope, bearing no address or writing of any sort.

"Dere's nodding aboudt der plue prints to helup us know somet'ing," said Carl. "Oben der enfellup, Matt."

"No," returned Matt, "we can't do that. That would be going a little too far."

"Vell, ve got to do somet'ing oof ve findt oudt who dose fellers vas."

"We'll wait, and give them a chance to claim their property."

"How dey vas going to glaim it, hey? Dey didtn't dell us who dey vas, und ve ditn't dell dem our names."

"We know the air-ship came from South Chicago. I don't believe there are very many air-ships in that place, and if we inquire around a little we ought to be able to find out who owns the Hawk."

"Righdt you vas! Somevay, Matt, you always know vat to do ven eferypody else iss guessing. Shall ve ged indo der car und go pack to der pig city py vay oof Sout' Chicago?"

"That's our cue. If we can discover who owns the Hawk we'll leave these papers there for him."

Matt rolled up the envelope and the papers and stowed them safely away in his pocket.

"I know dere vas some niggers in der vood-pile, all righdt," averred Carl. "Two fellers vouldn't go off mit an air-ship dey don'd know how to run oof eferyt'ing vas like it ought to be."

"There may be a whole lot of sense in what you say, Carl," replied Matt, "and then, again, the explanation of the queer layout may be extremely simple. Don't get to imagining things, old chap, but coil up that rope and throw it into the car. We'll carry it back to South Chicago and leave it at the same place we leave this roll of blue prints."

While Carl was coiling up the rope, Matt gave his attention to the automobile. When Carl arrived and threw the rope into the tonneau, Matt was busy with the crank.

Presently they were in the car and headed back along the return course.

Hardly had they got under good headway, however, when a flurry of dust showed in the road ahead of them. As the wind blew the dust aside, a horse and buggy with two men broke into view.

In accordance with the