Finally the last word was spoken, the planter shook hands with each of his visitors, Frank turned on the power, the aeroplane with the motor exhaust sounding like a volley of musketry started to run along the level ground, and presently, to the consternation of the entire gathering, began to climb upward, just like a creature of magic!

Cries of awe arose from scores of throats and to a man the peons threw themselves flat on their faces, hardly daring to look at the terrifying spectacle.

CHAPTER XV.

AN UNPLEASANT SURPRISE.

“At last, Frank, we’re on the move!”

“Yes,” replied the one at the wheel, as the cries and cheers from below were drowned by the volleying motor explosions; “and did you see the senor kissing his hand after us, while his men were flat on their faces?”

“It was a queer sight,” Andy remarked.  “And no wonder these ignorant peons call our little monoplane a ‘devil-bird.’”

“Look down now.  Just to think of two Yankee boys being allowed to swing over a tropical scene like that,” said Frank.

Both of them were deeply interested.  In the valley they could see the little town, with the river stretching off toward the south.  Then there were the patches of tropical vegetation, the fruit trees and the cocoa plantations—­all those interesting things which neither of them had ever set eyes on before.

Senor Mendoza had told them how the coffee was grown upon a certain part of the mountain slopes, since it did not do well in the valleys, preferring a higher altitude.

They followed the course of the river generally, intending to cover possibly something like eighty or ninety miles before trying to comb the land from side to side, in the endeavor to find the strange cliff enclosed valley.

From time to time Andy would call the attention of his aeroplane chum to some striking feature of the landscape far below.  The little Kinkaid motor was humming merrily, without ever missing a stroke, and Frank, having the utmost confidence in its steadiness now, after so many trial spins, could take a few seconds at a time to observe these things.

“When we’ve gone something close on an hundred miles direct,” remarked the pilot of the craft, presently, “I think we’d better make a descent, if given the chance.”

“You spoke of that before,” remarked his companion, anxiously.  “What is the reason for doing it, Frank?”

“Oh, nothing serious,” replied the other.  “We will then be at the parting of the ways, you know.”

“You mean we’ll be about to leave the river that will have been our guide up to then?” asked Andy.

“Yes,” Frank admitted.  “And from that time forward we must simply depend on our judgment for everything.  In that event it might be well if we looked over the entire plant, to make sure everything was in apple-pie shape.”