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 rightsgenerally on the storm-battered craft, was nothing loath to obey Nat’ssummons to the bridge. Ding-dong Bell announced that his engines werein good running order and could be left to themselves for a time. So itwas not long before they all, including Mr. Tubbs, were grouped ininterested attitudes about the man of science.

  “As Mr. Tubbs knows,” said the professor, “it was our original plan toresume our voyage on the _Tropic Bird_, following our observations andpicture making at the volcanic islands. Our destination was to be thecoast 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 forinterest. 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 is known to besituated on an island in the midst of a lake high up on an Andeanplateau in Bolivia.”

  “Like the one on Lake Titicaca in Peru,” said Nat.

  “Ah, you have read of that?” said the professor approvingly. “Yes, fromthe documents which came into the possession of the institute as thegift of a traveler in Chile, it is probable that the ruins which I amcommissioned to search for are very similar in character to those youhave mentioned.”

  “How are they to be reached?” asked Joe.

  The professor smiled.

  “From what we have been able to learn,” he said, “earthquakes havedestroyed the roads formerly used, and there is no way of reaching thelake by land——”

  “Then—then——” stammered Ding-dong helplessly.

  “One must fly to them,” said the professor as calmly as if he were in aclass-room. “Thanks to modern science, I believe it may be possible atlast to obtain pictures and priceless relics of that forgottencivilization.”

  “But where are you going to get an airship?” asked Nat, when he hadrecovered his breath.

  As for Joe and Ding-dong, they regarded the professor in silentamazement. Mr. George Washington Tubbs merely grinned. Clearly, theidea was no startling novelty to him.

  “That has been arranged for,” rejoined the professor. “A dirigibleballoon of the most modern type is already at Santa Rosa, a small townon the Chilian coast. Before leaving the States, I took some lessons inoperating such a craft; but really, that was hardly necessary, as Mr.Tubbs is a fairly expert operator of dirigibles, and has a knowledge oftheir construction and machinery.”

  “Then all that you will have to do, when you reach this town, is to getthe dirigible ready and then start the search for the lost city?”inquired Nat eagerly.

  “That is all. It should not take long, either. The machine is packed innumbered sections. For security it has been labeled ‘Merchandise,’ andis in charge of the American consular agent, who alone knows what theboxes really contain.”

  “Excuse me for saying so,” stuttered Joe; “but it sounds like—like awonderful fairy tale.”

  “It is one,” said the professor smilingly, “a fairy tale which, withthe aid of you boys, I hope to make true.”

  “With our assistance?” echoed Nat in an astonished tone.

  “Yes. I really believe that it was Providence that threw me in the pathof you boys. You are exactly the type of self-reliant, clever youngAmericans that I need for assistants in the work. Are you willing tocharter the _Nomad_ to me, land me on the South American coast, insteadof in California, and give me your services, for a substantialcompensation?”

  “I—I beg your pardon,” Nat managed to choke out, “but the idea is soentirely new to us that I think we shall have to hold a consultationfirst.”

  “Take your time,” said the professor airily; “take your time. It ischaracteristic of me to arrive at quick decisions, as Mr. Tubbs knows,and I don’t mind telling you that I shall be very disappointed if youdon’t see your way to accommodate me. We are now almost on a straightcourse for the coast of South America. If, on the other hand, we landedin Santa Barbara, I should have to take steamer from San Francisco toSouth America, and I might arrive too late.”

  “Why?” demanded Nat. “Is there any one else in search of the lost city?”

  “My colleagues fear so,” was the rejoinder. “The documents passedthrough many hands before they reached scientific ones, and thetreasures of the lost city, if they come up to all accounts, are enoughto tempt any one to search for them for their intrinsic value alone.”

  “Have you any idea who the men are who may prove your rivals?” askedNat.

  “I have—yes. But I do not wish to discuss that phase of the matter anymore just now. Suppose you and your friends hold your consultation andthen notify me of its result?”

  “Very well,” agreed Nat.

  Leaving the wheel in charge of the rubicund-headed Mr. Tubbs, who was acapable steersman—indeed, there didn’t seem to be much he couldn’tdo—the boys withdrew to Ding-dong’s domain—to wit, the engine room.

  They were below for about fifteen minutes.

  When they reappeared, Nat’s face bore a radiant expression. He walkedstraight up to the scientist, who was gazing at the sea with anabstracted look as he studied the various forms of life that werevisible in the clear water.

  “Well?” he asked, facing around, clearly anxious for “the verdict.”

  “Well,” repeated Nat with a smile, which was strangely at variance withhis words, “I regret to report that we cannot undertake the commissionyou proposed——”

  “What! You cannot? But I——”

  “That is,” continued Nat, “for any compensation. But we will agree toland you and your companion at the port you desire, and further thanthat, we will, from that time, place ourselves under your orders in thehunt for the lost city.”

  As Nat spoke these words, the dignified man of science actually caperedabout, and snapped his bony fingers in huge delight.

  As for Mr. Tubbs, he gave a wild “Hurr-oo!” of delight.

  “Hurrah for the Grigg’s expedition!” he cried.

  “Three cheers!” ordered Nat, and they were given with a will. Theechoes were still ringing out, when Nat gave a sharp exclamation, andpointed to the eastward.

  “A strange sail!” he cried, as they all turned eager eyes on thedistant speck of canvas.