know what you’re hinting at,” observed Dave shrewdly. “I suspected you were up to something when I saw you working over those little canvas bags. What’s the mystery, Hiram? Going to tell, this time?”

“I’m not,” dissented the young airman’s assistant staunchly. “You’d just laugh and say it was another of my grand schemes. All right! Those bags mean something—provided you go into this new contest. Honest, Dave,” went on Hiram with impressive earnestness, “I can put you onto a wrinkle in aeronautics that is new enough, and strong enough, to carry the day any time—oh, bother!”

Whatever scheme the young lad had in his mind, its disclosure was prevented at that moment by the arrival of an intruder. A man of about thirty, wearing a monocle, mincing in his steps and looking the typical English “dandy” to perfection, approached the bench where the two friends sat.

“It’s Lieutenant Montrose Mortimer,” remarked Dave with a faint smile.

“Lieutenant nothing!” declared Hiram forcibly. “He’s no more a British army officer than I am.”

“Ah, Mr. Dashaway,” spoke the newcomer, bowing, “I hope you’ve thought over my proposition.”

“Why, yes, Lieutenant,” replied Dave, “I have done so.”

“And have arrived at a decision?” questioned the other with marked eagerness.

“Well, no, not exactly,” answered Dave promptly. “You see, Lieutenant Mortimer, I am not a free agent in aviation matters. In fact, you might say I am under contract indefinitely to Mr. Brackett, who has financed me in the past. I should have to refer your offer to him, you see.”

“When will he be here?” asked the man, evidently very much disappointed.

“He may be here within a week.”

“I sincerely trust you will prevail on him to accept my offer,” spoke the pretended army man. “I shall feel that my duty to the admiralty and war office has been remiss if I fail to secure your valuable services. I am aware of your opposition to leaving your native country. I also appreciate your wish to remain neutral in regard to any actual warfare. That can be arranged. What we ask of you is to act as an instructor. Please think it over,” and he turned aside.

“Now, then,” broke out Hiram promptly as the lieutenant sauntered away, “what is that fellow really after, Dave?”

“Why, Hiram, according to his own story he is a representative from the aviation department of the British war office. He has made a very creditable showing—and he offers me all expenses paid abroad, where he says a yearly contract of several thousand dollars will be offered.”

“I don’t like him. Why, say, he reminds me of one of the funny cartoons that new tramp friend of yours drew for us last evening.”

“Hello!” exclaimed Dave, glancing hastily at his watch and then at the hangar. “He’s some sleeper; isn’t he, that tramp?”

The young airman referred to a new character who had incidentally come across their path the day previous. He was a tramp, a little above the average, but still frowsy, hungry and penniless. His humor had made an impression on the boys. They had fed him and he had asked for work to repay them. He was sober, and he looked honest, Dave had consented to his sleeping in the hangar.

“I guess it’s the first comfortable bed the poor fellow has had for a long time,” explained Hiram. “Say, Dave, he must have been a good artist once, to draw those faces as cleverly as he did last evening.”

“Yes, he certainly has a sort of genius about him,” began Dave, when there was a sudden and startling interruption.

From Dave’s hangar there came a dull explosion. Both of the young aviators made a rush in its direction, wondering what accident had happened.

CHAPTER II

“Somebody is trying to blow us up again!” shouted Hiram, in a great state of excitement.

That word “again” meant just what the young airman apprentice intended that it should. As we have already said, the two chums were no novices in the strange line of business activity they had taken up to earn a living. They had not only shared triumphs and gains, but many a peril besides. There had instantly come to Hiram’s mind, and to that of Dave Dashaway as well, on the present occasion a memory of past deeds of jealousy, hatred and cunning on the part of unprincipled rivals, where fire and powder were used in destructive and dangerous work.

There had been no lights in the hangar since the night before, its only occupant that the boys knew of was the tramp-artist they had accommodated. As both noticed a little puff of smoke shoot out through a ventilating pipe in the roof of the structure, they were sure that something had blown up, or had been blown up.

Hiram and Dave were greatly anxious. Inside that hangar were two machines valued as an expert horseman would cherish his pet steeds, or a crack motorist his favorite automobile. Particularly was Dave’s latest acquisition, the Ariel, to which Hiram had referred so proudly, a possession that the young birdman treasured. The active fear that this might have sustained some damage spurred him to hasten on and see what had happened.

It was by no easy or accidental route that Dave Dashaway had reached his present position as an aviator. It had been no path of roses for him. In the first book of this series, entitled “Dave Dashaway, The Young Aviator,” his struggles and initial triumphs have been depicted. He found a good friend in one Robert King, a man of some means, and by hard study and practice Dave won his laurels as a professional.

In the second volume, called “Dave Dashaway And His Hydroplane,” the further progress of the ambitious young airman is recited. His father had been a scientist and balloonist. The cooperation of one of his old associates proved a wonderful aid to Dave, and he went through some stirring experiences both up in the air and on the water.

“Dave Dashaway And His Giant Airship,” was the medium for telling of Dave’s breaking of many aviation records. In that book the flight of the dirigible Albatross, involved a fascinating series of discoveries and adventures. The last preceding book of the series, “Dave Dashaway Around The World,” describes a daring race for a rich prize, which Dave, with the willing aid of his young friends, won, honorably defeating all competitors.

Hiram Dobbs, a young aero enthusiast, Dave had picked up accidentally. It proved to be a lucky “find.” Crude, impetuous though he might be, Hiram was not only a loyal friend, but developed great efficiency as a sort of understudy of the chum and employer whom he looked up to as the ideal champion of the aviation world.

As the young airman had put it, he and his good-natured and well-intentioned assistant were now “taking a rest.” They had come to Midlothian, a practice field of a Mississippi river city, to be near several points where exhibition aviation features were in progress. Mr. Brackett had been the mainstay, financially, of Dave all through his professional career. It was true that the young aviator had essentially