Cliff gave him that tolerant smile which Johnny found so intolerable.  “It is not at all necessary.  I thought of all possible contingencies when I first saw the Thunder Bird.  Across the line the name absolutely identifies it, which is rather important.  On this side it is known as a bird fond of doing the unusual.  Your reputation, old man, may help you out of a tight place yet.  Now we are duck hunters, remember.  Hereafter we shall be hunting ducks with an airplane—­something new, but not at all improbable, especially when it is the Thunder Bird doing the hunting.  We must carry our shotguns along with us, and a few ducks as circumstantial evidence.  If we stray across the line accidentally, that will be because you do not always look where you are flying, and watch the landmarks.”

“This, of course, in case we are actually caught.  Though I do not see why that should happen.  They have no anti-aircraft guns to bring us down.  It may be a good idea to carry an auxiliary tank of gasoline in case of an emergency.”

“I don’t see why—­not if I fill up over there every time I land.  I can stay up three hours—­longer, if I can glide a lot.  Of course that high altitude takes more, in climbing up, and flying while you’re up there, but the distance is short.  I’ll chance running outa gas.  I don’t want the extra weight, flying high as we have to.  The motor’s doing all she wants to do, just carrying us.”

Cliff did not argue the point, but went out to his car, fussed with it for a few minutes, and then drove off on one of the mysterious trips that took him away from Mateo’s cabin and sometimes kept him away for two days at a time.  Johnny did not know where Cliff went; to see the boss, perhaps, and turn in what news he had gleaned—­if indeed he had succeeded in gleaning any.  Sometimes the long waits were tiresome to a youth who loved action.  But Johnny had been schooled to the monotony of a range line-camp, and if he could have ridden over the country while he waited, he would not have minded being left idle most of the time.

But he did not dare leave camp for more than half an hour or so at a time, because he never knew what minute Cliff might return and want him; and when one is being paid something like ten dollars an hour, waking or sleeping, for his time, one feels constrained to keep that precious time absolutely available to his employer.  At least, Johnny felt constrained to do so.  He could not even go duck hunting.  Mateo hunted the ducks, using Johnny’s gun or Cliff’s, and seldom failing to bring back game.  It would be ducks shot by Mateo which would furnish the circumstantial evidence which Cliff mentioned that morning.

Johnny went out to the Thunder Bird, shooed three kids from under the wings, and began to fuss with the motor.  One advantage of being idle most of the time was the easy life the Thunder Bird was leading.  The motor was not being worn out on this job, at any rate.