Besides, the trees happened to be much lower on this side, which fact would be of considerable benefit to them when they started to make the run, and rise.

Frank was still muttering the number of feet to himself, and had arrived within something like five yards of the nearest trees, when, without the slightest warning, he heard Andy let out a screech that could have but one meaning.

He had surely sighted something that spelled peril to one or both of the Bird boys.  Frank had wisely kept the rifle in his hand, and instinct caused him to throw this up to his shoulder, though as yet he had not the slightest suspicion as to what the nature of the danger might be, nor the quarter in which it lay.

CHAPTER XX.

THE AEROPLANE BOYS ONCE MORE AFLOAT.

“Frank!  Oh!  Frank!”

More than a few times had it fallen to Frank Bird to drag his cousin and chum, Andy, back from some impending danger.  Now the shoe seemed to be on the other foot.

Even as he looked hastily up, startled by these sudden cries, Frank felt his arm seized in a frenzied clutch, and himself jerked backward.

“What is it, Andy?  Here, hold on, let my arm free, and tell me!” he exclaimed.

“Look there; and you were going to walk right up against it!  Oh!  Frank, what a horrible monster!” Andy replied, in trembling tones, as he strove to point toward something that he had seen just in the nick of time.

“Whew!  I should say you were right!  Ain’t he a dandy, though?  And if I saw him at all, I thought it was a great big vine hanging from that tree!  Ugh! look at him stretch his mouth, would you?  Andy, thanks to your sharp eyes I’m here, instead of in his slimy folds.  I guess he could crush an ox.  They say nothing can stand the pressure, once they get a couple of folds around.”

“Is it a python?” gasped Andy, his horrified eyes glued on the spectacle of the slightly swaying ten feet of snake that hung from the limb of a great tree, in part as thick as Frank’s thigh.

“About the same thing,” replied Frank.  “Down here they call them anacondas, and in other parts of the world they’re boa-constrictors.  I guess the whole bunch belongs to the same family of squeezers.  But that fellow is in our way.”

“Well, yes, if you’re still determined to run the aeroplane across lots toward this side of the opening,” Andy remarked with a shudder.  “Why, perhaps that old chap might get gay, and grab hold, just when we expected to go sailing off.  That would be a calamity, not only for him, but the Bird boys in the bargain.”

“All right.  Then he’s got to get his,” Frank observed.

“What are you going to do?” demanded the other, nervously.

“Take a crack at his head,” came the reply.  “Once let a flat-nosed bullet from this little Marlin hard shooter smack him on the coco, and there’ll be a funeral in the anaconda family.”