HARVEY HAMILTON walked out to where his aeroplane was waiting, and under the eyes of Ann Harbor and her aunt set the propeller revolving, mounted his seat, called a cheery good-bye and sped away in the direction of Dawson. He had become so familiar with the section that there was no uncertainty in his course. He was not heading for the town, but veered slightly to one side, and when he caught sight of the workshop of Professor Milo Morgan, he aimed as straight for it as an arrow driven from a bow.  
He was yet some distance off when he observed the man in front of his building, bending over his helicopter as if attending to some repair of the machinery. When the noise of the approaching biplane fell upon his ear, he straightened up, turned around and stared in amazement. He stood as rigid as a statue, never once removing his gaze from the biplane, which lightly touched the ground, scooted a few rods and came to a standstill less than fifty feet from where he was scrutinizing it, and the young aviator.
 
Harvey knew the critical moment had come. While stepping to the ground, he drew his revolver from his hip pocket, examined it for a moment and then shoved it back in place. This was a little by-play meant to warn the Professor that his visitor owned a deadly weapon and held it at instant command. It is to be noted that the man carried nothing of the kind. His skill as a chemist gave him more frightful agents, though he could not have called them into play, as the circumstances stood, before the youth would anticipate him.
 
Harvey faced him with a smile and walked forward.
 
“Good morning, Professor; may I have a little talk with you?”
 
“Have you come to shoot me?” asked the man, with a terrible glare. He could not forget his recent experience at the cavern, when he must have believed he stood on the very edge of death.
 
“That depends upon yourself,” was the reply in the same pleasant voice; “I call upon you as a friend, but if you wish me to be an enemy I am prepared.”
 
“What do you want?”
 
Throughout the remarkable interview which followed, neither sat down, and Harvey held his place a dozen paces away. This was prudent, for[278] it was uncertain what the crank might attempt. So long as he was held off he could do no harm, for Harvey would forestall his slightest movement. The venomous hatred shown by him toward the youth because of his interference warned the latter to be on the alert, especially during the opening moments of their talk.
 
“I have a few words to say to you, Professor; are you willing to listen?”
 
“Say what you please, but if you had a grain of sense you would know better than to place yourself in my power.”
 
“I haven’t placed myself in your power and don’t intend to do so; don’t forget that. I wish to speak about your trip across the Atlantic.”
 
“Well?”
 
“It is too bad that Bohunkus was prevented from going with you, but you will admit that he has no right to leave home without the permission of Mr. Hartley, with whom he lives.”
 
“What has he got to do with it?” demanded the Professor, in a voice that sounded like the growl of a tiger.
 
“He is the master of Bohunkus; if you will get his consent, the colored lad will accompany you to Africa; nobody else will object.”
 
“Then why did you and that fellow with you[279] hold him back?” asked the Professor with an ominous gleam of his burning eyes.
 
“I have just told you the reason; we ought to have explained and I am sorry we forgot to do so. If you will sail down to Mootsport, see Mr. Hartley and persuade him to say yes, there will be no more trouble.”
 
“I shan’t do any such thing; I don’t care about the boy, only it made me mad to have you and the other scoundrel try to prevent my doing as I pleased.”
 
“We were rough,—I’ll admit it, and I beg to apologize.”
 
Harvey was striving his hardest to win the good-will of the lunatic. Having impressed him with the fact that he did not hold him in fear, the young aviator was striving to placate and soothe him.
 
“Now,” continued the caller, “every one must admit that you have made one or two of the most wonderful inventions of the century. Are you sure you can sail across the Atlantic with your machine?”
 
“Humph!” snorted the Professor, “you know I can; why do you ask such a question?”
 
“Suppose when you are well out over the ocean you run into a tempest or hurricane?”
 
“It will take me less than two days to cross and I can read the weather for that long; I know better than to run such a risk.”
 
“Good! but you know the weather probabilities sent out by the government are not reliable far out at sea.”
 
“I’m not depending on the government; I shall read the signs myself.”
 
“Good again! But suppose some part of your machinery breaks down.”
 
“It won’t break down; it is made too well and has been tested too often.”
 
“Or that that new kind of petrol or fluid should run short, owing to unexpected delays?”
 
&ldq............