“Right.  Go to the head of the class,” interrupted Stacy.

“Chunky, you keep out of this.  You’ll mix him up.”

“Guess somebody’s mixed up already,” retorted the fat boy.

“Five is right,” continued Tad.  Five dollars is what we owe you.  Is that clear now?”

“Si, señor.  But I work one week.  Juan earn ten dollar—­”

“I’ll tell you what to do,” interjected Ned.  “Start all over again.  You begin work to-day; Juan, and we’ll pay you ten dollars for every week from now on.  You haven’t worked for us before to-day, you know.”

The lads laughed heartily, but Juan merely showed his teeth, protesting that he had earned ten dollars.

“Here,” said Tad, thrusting a five dollar bill at him.  “You take this.  It’s all we owe you.  If you see any of your friends, you ask them how much we owe you.  They’ll tell you the Professor is right.”

Juan took the money greedily, still protesting that they owed him ten dollars, because he had worked a week.  Mounting his burro, he rode away; at once falling into the marvelous speed that he had shown them on the first day out.

The lads shouted with laughter as they saw burro and rider disappear among the foothills, both running for all they were worth, Juan uttering his shrill “yi-yi’s,” as he pedaled the ground.

That was the last they saw of the Mexican guide that day.  The rest of the day was employed in games, trick riding, rope throwing and the like.  Stacy found some horned frogs, which were of considerable interest to the boys.  Chunky made the discovery that the frogs liked to have their backs scratched with a stick, and the frogs of the foothills probably never spent such a happy day in all their lives as Chunky and his stick provided for them that afternoon.

Late in the day, it dawned upon the boys that Juan was still absent.  They consulted with the Professor about this, upon his return from a collecting trip along the foot of the mountains.  But the Professor was sure Juan would be in in time for supper.

Such was not the case, however.  After the meal had been finished Tad announced his intention of riding off in the direction Juan had gone, to see if the guide could not be found.

“I’ll go with you,” announced Stacy.

“All right; come along,” said Tad, tightening his saddle girths.  “We’ll have a fine gallop.”

“Be careful that you do not get lost, boys,” warned the Professor.

“Can’t get lost.  All we have to do is to follow the foothills.  We shall probably find Juan and his burro sound asleep on an ant-hill somewhere.  He’s positively the laziest human being I ever set eyes on.”

“Better take along five dollars to bait him with,” suggested Ned.

“I’ve got my stick,” said Stacy.  “I’ll tickle the back of the burro and its rider, just as I did the frogs.”

“You try that on the burro and he’ll kick you into the middle of next week,” warned Walter.