There was special reason why Dr. Byrd should feel more than ordinary interest in Mr. Miles. Both of them had long been enthusiastic collectors of souvenirs and curios of many kinds, and it was not long after their first meeting that each of them discovered the similarity of their hobbies. They were together frequently thereafter, both in the hospital and out of it. They talked of the places they had visited and the sights they had seen and the curios they had collected until it seemed almost that they must have been companions in all their travels and all their hunts.

Then Dr. Byrd pulled out some of his trunks, opened them and disclosed a wealth of treasures such as caused the eyes of the aviator to stand out big with astonishment. This treasure was not so remarkable in money value, perhaps; but it was indeed wonderful in novelty and abundance.

An idea of the nature of this collection may be presented by a description of a few samples. One of them was an oriental jewel casket of engraved rock and crystal mounted in enameled silver. Two other articles of special interest, because of their rarity, were a set of checkers made of sharks’ vertebrae and an “eye” from an Egyptian mummy case. This eye was made of bronze and black and white marble.

A long chapter could be devoted to a description of the doctor’s collection. As he exhibited them to Mr. Miles he handed over for inspection some Abalone pearls of California, blister pearls of Ceylon, a necklace of fluorescent amber from Sicily, jade ornaments, smoky quartz, Brazilian crystal balls, topaz from the Ural mountains, petrified wood, moss agate, rainbow agate, bloodstone from India, sardonyx from Uruguay, a Texan jasperized wood ornament, a jasper tray from the Ural mountains, fire opals, Norwegian sunstone, and an enameled talisman necklace.

Undoubtedly Dr. Byrd valued this collection much higher than a disinterested authority would have valued it, but there is little doubt also that it would have brought a considerable sum even at an auction sale. Nevertheless, the owner of Lakefarm could not throw off something of an air of sadness as he was exhibiting his treasured gems and curios.

“Two years ago,” he remarked to the aviator, “I could have shown you a collection that would have opened your eyes much wider. I then had a dozen other stones that were worth several times as much as all of these together, but they were stolen.”

“Did a burglar break in?” asked Mr. Miles.

“No, I wouldn’t feel so badly if they had gone in such manner. But it was a trusted employe that took them. He had been a teacher at the school for a year and I grew to like him exceedingly. He was really a brilliant fellow and I admired him. In fact, I gave him my full confidence. At the end of his year he resigned, and a few days later I discovered my loss.”

“Couldn’t you find him?” inquired Mr. Miles.

“Certainly. That’s what made it so hard to prove anything against him. He was the smoothest kind, all nerve and calculation.”

“How do you know he took them?”

“Didn’t you ever know anything you couldn’t prove?” replied the doctor slowly. “I knew who stole those gems the instant I found them missing. Immediately I saw his excellent qualities in a new light. He was an extremely clever hypocrite.”

“Did you meet him afterward?”

“No, I never saw him again. I put it up to the police. I told them of my suspicions, but couldn’t give them any information that tended to fasten guilt on Maxwell any more than on anybody else.”

“Maxwell was his name?”

“Yes. The police worked a while on the case, but gradually gave it up. Then I wrote to Maxwell and informed him plainly where my suspicion rested.

“He wrote a reply full of indignation and reproach, but it didn’t ring true. I’ve noticed the smartest rascals seem to be unable to seem entirely innocent when they know they are suspected. It’s a remarkable study, criminology. And yet, it’s as simple as A-B-C.”

“In what way?”

“Everything’s simple when you understand it, I’m ready to believe. If we could learn the secret of the universe, we’d be astonished to find out what a simple proposition it is.”

“You’re getting pretty deep,” smiled Miles.

“Perhaps I am. But I’m confident that the effects of dishonesty on the dishonest person are similar to the effects of the use of an untrue square in the construction of a building. He absolutely can’t help growing out of plumb. When you appreciate that rule, you will understand how I knew that Maxwell committed the theft.”

It was months after the resignation of Rodney Maxwell before the boys of Lakefarm learned of the stealing of the gems, and then the information came to them in a vague manner. Pepperill Humphrey let the first hint drop, and the curiosity of the young Scouts would not let him alone until he revealed some more of his information. Pepper had many good qualities, but he was very talkative, and did not require much pumping to set him going in earnest, and soon the secret ceased to be a secret.

The conversations between the doctor and Mr. Miles on the subject of their collections led to a move highly pleasing to the Boy Scouts of Lakefarm. Dr. Byrd had several times expressed a desire to explore the cave behind the waterfall, where the aviator’s lost bag of souvenirs had been found. To both of them this cave was a place of some mystery, and naturally they felt considerable interest in a solution.

“I’d like to know how that bag got in there,” said the doctor one day. “And the first step toward finding out must consist of an inspection of the cave and its immediate vicinity.”

“I agree with you,” returned Miles. “I’d like to go with you when you inspect the place, but it’ll be a week or two before I can stand any vigorous exercise.”

“It seems to me that you’re entitled to accompany the first expedition of discovery,” continued the doctor slowly. “But, as you say, you won’t be able to move about in a lively manner for some time. Now, I have a plan. It’s been working in my mind for several days, and I’ve about decided to put it into execution.

“It is this: Mummy CaÑon is really a remarkable place. It’s a wonder to me that it hasn’t been exploited as a resort long before this. I’m seriously considering, Mr. Miles, a plan to purchase the whole of the caÑon from the government and to enter on an extensive real estate project.

“Of course I’ll incorporate, but I propose to retain a controlling interest in the stock company. I’ll buy the land, get out my incorporation papers, and then invite some eastern promoters here to look at my proposition.

“I’m dead sure the thing could be made a success. The D. and R. G. railroad is about to run a short line this way, and with a little advertising we’d soon have all the people out here we could take care of. A hotel, some cottages, and conveniences for sportsmen and sight-seers ought to start things humming.

“And the cave would be an important attraction. But it must be made accessible. So I have planned to give the boys a little experience in bridge and road engineering. I want to construct a foot bridge over the river near the rapids and dig a walk along the steep western bank right up to the cave. I would put up railings to make it safe and a well-protected bridge from the bank through the fall into the cave.”

“That’s a great idea!” exclaimed Miles, enthusiastically slapping his sound leg. “When are you going to begin work?”

“In a day or two. I’ve so nearly decided to put the big scheme into operation that I’ve already begun action on the smaller one. The lumber for the bridges and railing will be delivered at the caÑon to-morrow.”

“Good! I’m heartily in sympathy with the work. The boys will like it too.”

“Oh, I’ve had the boys in mind all the time,” declared the doctor warmly. “The young Scouts of Lakefarm, I intend, shall have much to do in the building up of Mummy CaÑon. The work will be full of lessons in engineering, construction and business.”

Of course the boys were delighted when they were informed of this plan. The doctor did not tell them of the larger scheme he had in view, as that was not yet fully decided upon.

A few days later work was begun. The lumber had been delivered at the shallow place near the head of the rapids, which was the place selected for bridge number one. The stream was wide at this place, but this width suited the purpose of Dr. Byrd the better, for he desired a task worthy of the efforts of forty-four energetic boys.

First, it was necessary to put in foundations for the abutments and supports of the bridge. This was done by gathering stones and bowlders and wedging them in place as securely as possible. Then followed the task of sawing the timbers into proper lengths, according to plans that had been prepared under the supervision of Mr. Frankland and Mr. Porter. This done, the frame work was put up and the planks nailed down and the railings placed.

It was really a very satisfactory piece of work. First of all, it was stable and safe to walk upon. Second, it presented a neat appearance. Third, the boys had done it all themselves.

The bridge was finished in two working days. The doctor, in mapping out the program, provided for alternate days of work at the river and study at the school, so that three days elapsed before the bridge was completed. Then another day was spent at their books, after which the boys returned to the caÑon and began making a level foot-path along the steep western bank of the river.

This was done in short shifts in order that the work might be pushed rapidly without fatigue. Half a dozen picks and shovels were kept swinging vigorously and the way the earth and stones went flying into the river said the work would soon be done.

Two weeks after the starting of the work on the larger bridge the entire work was finished. There was a strong railing on the river side of the path and a narrow well-protected bridge through the waterfall to the cave behind. It was nearly night when the last nail was driven, and as they had no lanterns with them, it was decided not to explore the cave on this occasion, but to reserve this inspection for a special excursion on a later day.

That evening at Lakefarm, however, something happened that was destined to bring about a decided change in the program with reference to this plan. The person most affected was Hal Kenyon. It meant trouble for him and some extremely perilous adventures for some of the boys.

In the wash room Hal drew a handkerchief from his pocket, and as he did so something heavy and metallic hit the floor. Several of his schoolmates heard the sound, and Pickles sprang forward and picked up the object. As he did this, Hal also made a spring and attempted to snatch it away from Pickles.

The latter, however, with no uncivil intent, edged away, at the same time gazing eagerly at the small, heavy object in his hand.

“Oh, Hal, it’s gold!” he exclaimed. “Where did you get it?”

“What’s that?” inquired a voice that chilled Kenyon through, and, looking up, he saw Mr. Miles advancing toward them. He had discarded his crutches and was using a cane.

He held out his free hand toward Pickles, who, like one hypnotized, delivered the object of interest to the aviator. The latter looked at it eagerly for a moment, then fastened his eyes on Hal with searching gaze.

“Boy,” he said sternly after a moment’s silence; “this nugget is mine. I thought you said—”

He did not finish the sentence, for Hal’s face had become so pale that it seemed as if he was going to faint.