the latter quality to a degree.
“Just as I thought,” said the professor finally, “your instruments have been deflected. But we will set them right at noon. A few simple adjustments, that is all. But I find that you have kept them in wonderful shape, considering your rough and trying experiences.”
“We have always tried to,” said Nat. “We knew how much depended on them.”
“And yet,” mused the professor, with his eyes fixed intently on Nat, as the lad stood at the wheel, “without the ability to understand them, those instruments would be worthless. Conradini, the Italian explorer, learned that.”
“At the expense of his life,” put in Nat. “The lesson was lost.”
“Ah, you have heard of Conradini?” asked the professor, in seeming surprise.
“I have read of him in that pamphlet on aerial exploration issued by the Italian Royal Society,” was the reply.
The professor readjusted his glasses. In his astonishment, he almost lost his latest piece of headgear – loaned him by Ding-dong. It was a not too reputable-looking Scotch tam o’shanter.
“You have a knowledge that surprises me in one so young,” he declared at last. “You take an interest in exploration, then?”
“That was the object of the Motor Rangers, when first we founded them,” declared Nat. “I think,” he added, with a twinkle in his eye, “that we’ve had our fair share of adventure.”
“From what you have told me of your enterprises, I agree with you,” assented the professor warmly. “But you have not told me yet of the future.”
“How do you mean?” asked Nat.
“I mean, what plans have you ahead of you? What do you intend to do next?”
The question came bluntly. Nat answered it with equal frankness.
“I really don’t know,” he said. “As you are aware, though, our course is now laid for Santa Barbara.”
“So you said last night, when you kindly offered us a passage home,” said the professor.
He paused for an instant, and Nat swung the Nomad’s bow around a trifle more to the south.
“Have you no plans for further adventurous cruises or auto trips?” pursued the man of science.
Nat laughed.
“I guess we’ve had our fill of adventure for a time,” he said; “that cleft between the volcanic islands nearly proved our Waterloo.”
“Nonsense; such lads as you could not live without adventure,” admonished the professor, making a frantic grab at his hat, as a vagrant wind gave it a puff that set it rakishly sidewise above one ear. “Do you mean to say that you feel like settling down to humdrum life now, after all you have seen and endured?”
“I guess we all feel like taking a rest,” said Nat. “We have had a fairly strenuous time of it lately.”
“Granted. But it has put you into condition to weather further times of stress and trial. Ever since we had that talk last night about the Motor Rangers, and what they have accomplished, it has been in my mind to broach a proposition to you.”
“To us?” temporized Nat. “I don’t see where we could be of any use to Professor Thaddeus Grigg, the most noted scientist of investigation of this age.”
The professor raised a deprecatory hand.
“As if you had not been of the highest service to me and to my companion already,” he exclaimed. “Had it not been for you, we might have – oh, well, let us not talk about it. That coward of a captain – ”
He broke off abruptly. Nat waited for him to resume speaking.
“What I wanted to approach you about was this,” resumed the professor, after a minute. “From the moment I met you, you appeared to me to be self-reliant, enterprising boys, who mixed coolness and common sense with courage. Such being the case, you are just the combination I have been seeking for, to carry out a project which awaits me on my return to America. It is a scheme involving danger, excitement and rich rewards.”
He paused impressively. In spite of himself, Nat’s eyes began to dance, his pulse to beat a bit faster. Adventure was as the breath of life to the young leader of the Motor Rangers, and, to tell the truth, he had faced the prospect of a life of inactivity with mixed feelings.
“Well, sir?” was all he said, however.
The scientist continued, with apparent irrelevance.
“You three lads, from what you have told me, have operated motor cars, motor boats, and endured much in both forms of transportation?” he asked.
Nat nodded.
“I guess we’ve had our share of the rough along with the smooth,” he said briefly, but he was listening closely.
“What would you say to trying a voyage in the air?” was the question that the man of science suddenly launched at him without the slightest warning.
Nat glanced up from his steering amazed. The scientist met the lad’s gaze firmly.
“Well?” he demanded.
“I – I – upon my word, I don’t know,” stammered Nat.
For once in his life, the young leader of the Motor Rangers was fairly taken aback.
CHAPTER VII.
A STRANGE SAIL APPEARS
“I am perfectly serious,” resumed Professor Grigg solemnly.
“The idea was such a new one that I admit it staggered me a bit,” explained Nat hastily.
“Suppose you summon your friends, and I will explain in more detail,” rejoined the professor.
Joe, who was polishing up the brass work and putting things to rights generally on the storm-battered craft, was nothing loath to obey Nat’s summons to the bridge. Ding-dong Bell announced that his engines were in good running order and could be left to themselves for a time. So it was not long before they all, including Mr. Tubbs, were grouped in interested attitudes about the man of science.
“As Mr. Tubbs knows,” said the professor, “it was our original plan to resume our voyage on the Tropic Bird, following our observations and picture making at the volcanic islands. Our destination was to be the coast of Chile. From there we were to go in search of a lost Inca city, which is described in documents recently discovered.”
“G-g-g-g-g-gee wer-w-w-w-whiz!” sputtered Ding-dong.
“Hush!” admonished Nat, who could hardly attend to his steering for interest. As for Joe Hartley, his eyes fairly bulged in his head.
“A lost Inca city,” he murmured. “Sounds good to me.”
“Is nothing known of the location of the place?” inquired Nat.
“Not except in a general way,” was the reply. “It
