“Never met the gentleman.”

“Then your name is not Alvin Baker?”

“Maybe you know my name better than I do.”

“No, but I know just as well as you do that you are not Alvin Baker.”

“How do you know that?”

“Because Alvin Baker is my cousin.  I am Hal Stone, and I live in Oswego, New York.”

“I do not believe you.  You are an impostor.”

“Let me tell you a secret.  I have penetrated your plot.  You are an enemy of my cousin.  There was no wager between him and you, but you don’t want us to find him.  You had better keep out of the atmosphere or I will have you arrested on a charge of disorderly conduct in the air.”

No answer.

“V A X, V A X, V A X,” called Hal.

Still no reply.

“I cornered him, proved he was an impostor, and now he won’t talk to me any more,” said Hal, addressing his companions.  Then he translated the code conversation, just completed, for the benefit of Mr. Perry.

“Well, that disposes of him for the time being, at least,” was the latter’s comment.

“But leaves a mystery as to his identity,” put in Bud with a “mystery smile”.

“No, I don’t think there’s any question as to his identity.”

“Have you worked it out by mathematics, dad?” Cub inquired.

“Yes, by sines and cosines.”

“What are sines and cosines?” asked Hal.

“You’ll find out when you go to college and study trigonometry,” Mr. Perry replied.

“Oh, I’ve seen those words,” Cub answered, with some of his alleged characteristic “highbrow eagerness”.  “You spell sine, s-i-n-e, and cosine, c-o-s-i-n-e.”

“Exactly,” smiled Mr. Perry.  “Those are terms used in higher mathematics.  But, in order that you youthful minds may not work too hard over my trick, I’ll admit that in my mind I spelled sine s-i-g-n, and cosine, c-o-s-i-g-n.”

“No use to try to get ahead of my father,” Cub declared, shaking his head.  “He could prove that water runs uphill by mathematics.  He means the signs and cosigns indicate that—.  What do they indicate, dad?  We got off the question just because you wanted to carry your point with a pun.”

“I meant to say that this fellow whom you cornered and chased out of the air is one of the fellows who hazed Hal’s cousin by marooning him on this island,” Mr. Perry answered.

“Gee! that never occurred to me,” exclaimed Cub, swinging his long arm with a snap of his finger like the crack of a whip.  “I bet anything you’re right.”

“We get one step nearer every time we make a move,” said Bud eagerly.

“Yes, but the question is, how many steps do we have to take before we settle this—­this—­mystery?” Cub demanded.

“Don’t look ahead so far,” Mr. Perry warned.  “Here’s a rule in such matters that applies to all men—­and boys—­of small or large capability.  Be careful never to look ahead so far you can’t see the step you are in the act of taking.”