While all this talk about gold and emeralds and bushmasters was going on in Big Jim's big house, over in a little house on the tiptop of Yelpin Hill, Jud Adams, the old trapper, was just sitting down to supper with two of his best friends. One of these was Will Bright, a magnificently built boy of eighteen with copper-colored hair and dark blue eyes, and the other his chum, Joe Couteau, silent, lithe, and swart as his Indian ancestors. Jud himself was not much over five feet tall, with bushy gray hair and beard and steel-sharp eyes. These three, with Fred Perkins, the runner, had won their way to Goreloi, the Island of the Bear, and brought back Jim Donegan's most prized gem, as already chronicled in "The Blue Pearl." They had learned to care for one another as only those can who have fought together against monsters of the sea, savage beasts, and more savage men. Joe and Will, moreover, had shared other life-and-death adventures together, as told in "Boy Scouts in the Wilderness," and, starting without clothes, food, or fire, had lived a month in the heart of the woods, discovered the secret of Wizard Pond, and broken up Scar Dawson's gang of outlaws. Will never forgot that Joe had saved him from the carcajou, nor Joe that it was Will who gave him the first chance of safety when the bloodhounds were hot on their heels through the hidden passage from Wizard Pond. Each one of the four, as his share of the blue pearl, and the sea-otter pelt brought back from Akotan, had received fifteen thousand dollars. Fred had invested his money in his brother's business in Boston, left Cornwall, and bade fair to settle down into a successful business man. Will and Joe had both set aside from their share enough to take them through Yale. As for Jud, the day after he received his winnings in the game which the four had played against danger and death, he had a short interview with his old friend Mr. Donegan.

"All my life long," began Jud, "I've been makin' money; but so far, I haven't got a cent saved up. I know how to tame 'most any other kind of wild animal, but money allers gets away from me. They do say, Jim," went on the old man, "that you've got the knack of keepin' it. Probably you wouldn't be worth your salt out in the woods, but every man's got somethin' that he can do better 'n most. So you just take my share of the blue-pearl money an' put it into somethin' safe an' sound that'll bring me an income. You see, Jim," he went on confidentially, "I ain't so young as I used to be."

"I should say you ain't!" exclaimed Big Jim, knowing how Jud hated to be called old. "You're 'most a hundred now."

"I ain't! I ain't!" howled Jud, indignantly. "I ain't a day over fifty – or thereabouts."

"Well, well," said his friend, soothingly, "we won't quarrel over it. I'll take care of your money and see that you get all that's comin' to you for the two or three years which you've got left"; and with mutual abuse and affection the two parted as good friends as ever.

To-night the old trapper and his guests had just finished supper when the telephone rang.

"Jud," came Mr. Donegan's voice over the wire, "what would you and Bill and Joe think of another expedition – after emeralds this time?"

"We'd think well of it," returned Jud, promptly. "The kids are here at my house now."

"Good work!" exclaimed the lumber-king. "All three of you come right over. I've got a scientist here who's going to guide you to where the emeralds grow."

"You got a what?" queried Jud.

"A scientist!" shouted Big Jim, "a perfesser. One of those fellows who know all about everything except what's useful."

"We'll be right over," said Jud, hanging up the receiver and breaking the news to his friends.

"Listens good," said Will, while Joe grunted approvingly.

"It's a pity old Jim ain't young and supple enough to go on these trips with us himself," remarked Jud, complacently.

"He ten years younger than you," suggested Joe, slyly, who always delighted in teasing the old trapper about his age.

"Where do you get such stuff?" returned Jud, indignantly. "Jim Donegan's old enough to be my father – or my brother, anyway," he finished, staring sternly at his grinning guests.

"You're quite right, Jud," said Will, soothingly. "Let's go, though, before that scientist chap gets away."

"He no get away," remarked Joe, sorrowfully, who had listened to the telephone conversation. "He go with us."

"I don't think much of that," said Jud, wagging his head solemnly. "The last perfesser I traveled with was while I was prospectin' down in Arizona. He sold a cure for snakebites an' small-pox, an' one night he lit out with all our cash an' we never did catch him."

Half an hour later found the whole party in Mr. Donegan's study, where they were introduced to Professor Ditson.

"What might you be a perfesser of?" inquired Jud, staring at him with unconcealed hostility.

The other stared back at him for a moment before he replied.

"I have specialized," he said at last, "in reptiles, mammals, and birds, besides some research work in botany."

"Didn't leave out much, did you?" sneered Jud.

"Also," went on the professor, more quietly, "I learned early in life something about politeness. You would find it an interesting study," he went on, turning away.

"Now, now," broke in Mr. Donegan, as Jud swallowed hard, "if you fellows are going treasure-hunting together, you mustn't begin by scrappin'."

"I, sir," returned Professor Ditson, austerely, "have no intention of engaging in an altercation with any one. In the course of collecting-trips in the unsettled portions of all four continents, I have learned to live on good terms with vagabonds of all kinds, and I can do it again if necessary."

"Exactly!" broke in Mr. Donegan, hurriedly, before Jud could speak; "that certainly shows a friendly spirit, and I am sure Jud feels the same way."

"I do," returned the latter, puffingly, "just the same way. I got along once with a perfesser who was no darn good, and I guess I can again."

"Then," said Mr. Donegan, briskly, "let's get down to business. Professor Ditson, show us, please, the map and manuscript with which you located Lake Eldorado."

For reply, the gaunt scientist produced from a pocket a small copper cylinder, from which he drew a roll of yellowed parchment. Half of it was covered with crabbed writing in the imperishable sepia ink which the old scriveners used. The other half was apparently blank. The lumber-king screwed his face up wisely over the writing.

"H'm-m," he remarked at last. "It's some foreign language. Let one of these young fellers who're going to college try."

Will took one look at the paper.

"I pass," he said simply; while Joe shook his head without even looking.

"You're a fine lot of scholars!" scoffed Jud, as he received the scroll. "Listen now to Perfesser Adams of the University of Out-of-Doors."

Then, to the astonishment of everybody, in his high-pitched voice he began to translate the labored lines, reading haltingly, like a school-boy:

"I, Alvarado, companion of Pizarro, about to die at dawn, to my dear wife Oriana. I do repent me of my many sins. I am he who slew the Inca Atahualpa and many of his people, and who played away the Sun before sunrise. Now it comes that I too must die, nor of the wealth that I have won have I aught save the Secret of Eldorado. On a night of the full moon, I myself saw the Golden Man throw into the lake the great Emerald of the Incas and a wealth of gold and gems. This treasure-lake lies not far from Orcos in which was thrown the Chain. I have drawn a map in the way thou didst show me long years ago. Take it to the king. There be treasure enough there for all Spain; and through his justice, thou and our children shall have a share. Forgive me, Oriana, and forget me not.

Alvarado"

There was a silence when he had finished. It was as if the shadow of the tragedy of that wasted life and vain repentance had drifted down the centuries and hung over the little company who had listened to the reading of the undelivered letter. The stillness was broken by Mr. Donegan.

"Where did you learn to read Spanish, you old rascal?" he inquired of Jud.

"Down among the Greasers in Mexico," chuckled the latter, delightedly.

"What does he mean by 'playing away the Sun' and the 'Chain'?" asked Will, of the scientist.

"When the treasures of the Incas were divided," explained Professor Ditson, precisely, "Alvarado had for his share a golden image of the sun over ten feet in diameter. This he gambled away in a single night. The Chain," continued Professor Ditson, "surrounded the chief Inca's residence. It was made of gold, and was two hundred and thirty-three yards long. It was being carried by two hundred Indians to Cuzco to form part of the chief's ransom – a room filled with gold as high as he could reach. When the gold came to his shoulder, he was killed. At the news of his death, the men who were bringing the Chain threw it into Lake Orcos."

"But – but," broke in the lumber-king, "where is the map? If you've got it with you, let's have a look at it."

Without speaking, Professor Ditson reached over and took the match from the table. Lighting it, he held the flame for an instant close to the parchment. On the smooth surface before their eyes, suddenly appeared a series of vivid green lines, which at last took the form of a rude map.

"What he learned from Oriana," explained Professor Ditson, "was how to make and use invisible ink."

"Fellows," broke in Mr. Donegan, earnestly, "I believe that Professor Ditson has found Eldorado, and I'm willing to go the limit to get one of the emeralds of the Incas. I'll finance the expedition if you'll all go. What do you say?"

"Aye," voted Will.

"Aye," grunted Joe.

"I assent," said Professor Ditson, with his usual preciseness.

Jud alone said nothing.

"How about it, Jud?" inquired Big Jim.

"Well," returned Jud, doubtfully, "who's goin' to lead this expedition?"

"Why, the professor here," returned the lumber-king, surprised. "He's the only one who knows the way."

"That's it," objected Jud. "It's likely to be a rough trip, an' treasure-huntin' is always dangerous. Has the perfesser enough pep to keep up with us younger men?"

Professor Ditson smiled bleakly.

"I've been six times across South America, and once lived among the South American Indians for two years without seeing a white man," he remarked acidly. "Perhaps I can manage to keep up with an old man and two boys who have never been in the country before. You should understand," he went on, regarding the old trapper sternly, "that specialization in scientific investigation does not necessarily connote lack of physical ability."

Jud gasped. "I don't know what he means," he returned angrily, "but he's wrong – specially that part about me bein' old."

"I feel it is my duty to warn you," interrupted Professor Ditson, "that this trip may involve a special danger outside of those usual to the tropics. When I was last in Peru," he went on, "I had in my employ a man named Slaughter. He was an expert woodsman, but sinister in character and appearance and with great influence over the worst element among the Indians. One night I found him reading this manuscript, which he had taken from my tent while I was asleep. I persuaded him to give it up and leave my employ."

"How did you persuade him?" queried Jud, curiously.

"Automatically," responded Professor Ditson. "At least, I used a Colt's automatic," he explained. "His language, as he left, was deplorable," continued the scientist, "and he declared, among other things, that I would have him to reckon with if I ever went again to Eldorado. I have no doubt that through his Indian allies he will be advised of the expedition when it reaches Peru and make trouble for us."

"What did he look like?" inquired Mr. Donegan.

"He was a giant," replied Professor Ditson, "and must have been over seven feet in height. His eyebrows made a straight line across his forehead, and he had a scar from his right eye to the corner of his jaw."

"Scar Dawson!" shouted Will.

"You don't mean the one who nearly burned you and Joe alive in the cabin?" said the lumber-king, incredulously.

"It must be," said Will. "No other man would have that scar and height. I'll say 'some danger' is right," he concluded, while Joe nodded his head somberly.

"That settles it!" said Jud. "It's evident this expedition needs a good man to keep these kids out of trouble. I'm on."