Chapter III.--JUST A TYPEWRITER RIBBON.

  "I don't understand what question he is asking," Jack said, "but I knowhow he makes the signal. He has an electric flashlight, and he tips theplane--the upper plane--forward, like he was plunging to the earth, andwrites the interrogation mark on the under side with the flame of theflashlight. See? Then it shines through the canvas and we read it! Greatidea!"

  "That must be the way of it," Frank said, "but what does he want? Andhow does he expect us to answer?"

  "If I was up there in the dark on a contraption like that," Pat said,"I'd be asking how I was going to find a landing place."

  "Sure!" Frank cried. "Ned wants to know where we are, and whether it issafe for him to make a landing. Dunderheads! Why didn't we think of thatbefore? He is passing now, and may not come back again."

  The light flashed by at swift speed, whirled, ascended several hundredfeet, and came over the plateau, repeating the signal. Then it settleddown into a steady circling of the camp.

  "He knows where we are, all right," Pat said. "What he wants to know isif it is safe for him to make a landing. If I ever go up in one of thosethings I'll drag a rope so I can climb down it."

  "I'll tell him what he wants to know," Frank said, "if you'll get me along stick on fire most of its length."

  "Wigwag?" asked Jack.

  "Sure!" was the reply. "Now," Frank continued, "build four fires, one oneach edge of the plateau. That will show him how large the place is.Then I'll take the flaming stick and wigwag o.k. Ned'll understandthat."

  Pat watched the wigwag signal with interest.

  "I saw foolish signs like those in the Philippines," he said, with agrin. "The natives use them to talk treason to each other. I've heardthat the same method is used by the East Indians who talk from onemountain top to another faster than words on a wire. How does he makethe o.k. signal?"

  "O is one left, followed by one right," Jack replied, "and k is left,right, left, right. You won't think the signs are foolish when you seehow quickly Ned reads them. See! He's shooting away now."

  "Perhaps he thinks the signals are being made by savages," Pat said.

  The aeroplane darted off to the west for half a minute, then whirled andcame back. The boys could not see the great 'plane distinctly, but thelights which burned on the front were bright and clear, so they saw thatthe 'plane was sweeping toward the earth as it advanced in theirdirection.

  "I don't believe many professionals would care to make a landing likethis," Frank said, as the machine dipped and slid to the ground, exactlyin the center of the plateau.

  "Hello, Ned!" he yelled, as the aeroplane rolled over the smooth surfacefor an instant and stopped.

  In a second the three boys were gathered about the machine, pulling atthe hands and feet of the daring riders. Jimmie McGraw bounded to theground as soon as he could cast off the lines which had held him to hisquivering seat.

  "Say," he cried, "you got a fire here? I'm most froze."

  Indeed the little fellow's teeth were chattering.

  "Cold?" echoed Pat. "We're melting down here. You're scared, that'swhat's the matter with you. You're scared stiff."

  Jimmie made a run for the speaker but brought up at the fire where thesupper had been cooked.

  "Here's comfort!" he cried, extending his hands out over what was leftof the small blaze. "The next time you get me up in the air I don't go!I've been freezing for an hour."

  In the meantime Ned Nestor was caring for the aeroplane, looking afterthe delicate machinery and covering it carefully with a huge oil-cloth.Pat stood watching the work with a grin on his face.

  "Are you thinking of giving me a ride in that thing?" he asked.

  "Not to-night!" laughed Ned.

  "Well, when you get ready for me to ride the air," Pat said, "just tellme the night before, and I'll shoo myself into the hills. If I'm goingto fall off anything, I'll take the drop from something solid, like amountain top."

  "No danger at all, when you know how to operate the machine," Nedreplied. "There's danger in running anything if you don't know how, evena sewing machine."

  "Where did you pick it up?" asked Frank.

  "He didn't pick it up at all," interposed Pat. "It picked him up."

  "I found it at Missoula," was the reply, "all packed and stored away ina freight warehouse. I had to get it out at night, and so lost time. Thepeople would have kept me there until now giving exhibitions if I hadshown up during the day."

  "But you did leave there in the daytime," urged Jack. "You were never inthe air since last night."

  "We left early this morning," was the reply, "and I was well up in thesky before many of the people saw me."

  "I never knew you could run one," Frank said.

  "Oh, I had some instructions from the Wrights," was the modest reply,"and, besides, there was an expert at Missoula who helped me get themachine together and contributed a few parting instructions."

  "Then you've been in the air all day?" asked Pat.

  "No, we stopped several times, of course, once on the right of way ofthe Great Northern railroad and filled our gasoline tanks," was thereply, "and rested there a few hours. Jimmie had to eat there, ofcourse!"

  "Eat!" came the boy's voice from the fire. "If I ever get a bite at foodagain it will drop down into the toes of me shoes! Here!" he shouted, asPat produced a can of pork and beans and started to open it. "Youneedn't mind opening that! I'll just swallow it as it is."

  "Bright boy!" laughed Pat, handing him a liberal supply of beans andfried bacon. "Now fill up on that and then loosen up on your impressionsof the sky."

  "I thought I'd make an impression on the earth before I got through,"Jimmie mumbled, his mouth full of beans. "We went up so far that themountains looked like ant hills, didn't we, Ned?"

  "About 7,000 feet," was the reply. "You see," he added, turning toFrank, "I wanted to size up the situation before I landed. If there isanybody in this upturned country at all, our presence here is known. Theaeroplane's chatter took good care of that. And, besides, our landing inthe night, with the lights going, gave unmistakable evidence ofsomething stirring."

  "I should say so," Frank agreed.

  "And so," Ned went on, "I wanted to learn if there were people abouthere, so I might visit them in the morning and put up the bluff of BoyScouts playing with an aeroplane in the woods. We can't attempt anythingin the mysterious line," he went on. "We've got to be entirely frankabout everything except the business we are here on."

  "Well," Frank said, "we found people here to-day and called on them."

  "What sort of people?"

  "Well, they seemed to have good broad backs," laughed Frank.

  "They ran away from you?" asked Ned, in surprise. "I should think theywould have proved inquisitive. Where were they?"

  "Down by Kintla lake."

  "Indians?" asked Ned.

  Then Frank told the story of the visit to the shore of the lake and thecavern, taking good care to describe the surroundings as closely aspossible. Ned laughed when the boy came to Jack's adventure in thehidden chamber.

  "I say it is some deserted mine," Pat declared, when Frank had concludedthe recital. "What else could it be?"

  "Robber's nest!" suggested Jack.

  Ned remained silent for a moment and then abruptly asked:

  "What kind of footwear made those heelless prints?"

  "You may search me!" Jack cut in.

  "Must have been Indian moccasins," Frank observed.

  Jimmie, who had been standing by the small fire, listening to the talk,now advanced to the little circle about the machine and uttered oneword: "Chinks!"

  "It is always Chinks with Jimmie," grinned Frank. "When there is acyclone in New York the Chinks are to blame for it, if you leave it tohim."

  "What would Chinks be doing up here?" demanded Pat.

  "Don't they get gold by washing it out?" asked Jack, with a nudge atJimmie's side. "Perhaps they're going to start a laundry!"

 
While this chaff was in progress Ned stood looking thoughtfully in thedirection of the lake. Not a word did he say regarding the sudden andbrief communication Jimmie had presented.

  "Any forest fires in sight?" asked Pat, finally breaking the silence.

  "Not one," Jimmie answered. "I would have dropped into one if it hadcome my way. It was fierce up there!"

  "It is rather cool when you get up a couple of miles," Ned laughed, "andJimmie wouldn't listen to reason regarding his clothes. To-morrow I'llgive one of you boys a ride, and you may see for yourself."

  "Not me!" Pat exclaimed. "I'll stay below and help pick up the pieces."

  "I should like to go," Frank said. "We may find the people we saw in therowboat. When we become acquainted with them we may be able to learnsomething about that cavern."

  "I would advise remaining silent about the cavern," Ned said. "It may beused for some criminal purpose, and we must not admit that we know ofits existence. We are just carefree lads, here for an outing, remember,"he added, with a laugh, "and we are due to make friends with everybodywe come across."

  "But you made us lug all this camping outfit up here," complained Jack,"so the men who steered the burros up the hills wouldn't know where wecamped. What about that?"

  "I thought it best to cut off all communication with the people below,"explained Ned. "It may be that the purpose of our visit here issuspected. In that case some one from below might want to find us--forno good purpose. So we'll keep out of sight of the people in the towns,unless they see our aeroplane, and cultivate the acquaintance of thenatives--if there are any."

  "How about gasoline and provisions?" asked Pat.

  "I have plenty of gasoline stored on the right of way of the GreatNorthern railroad," Ned replied, "enough to last us a month. It waspiped into a hidden tank from an oil car by a train crew now out of thestate. We are to get provisions at the same place, if we need more, forUncle Sam fixed all the details for us. All we have to do is to find thefellows who are setting forest fires and bring them to punishment."

  "We ought to locate every little smudge, with that aeroplane," Franksuggested.

  "That is my idea," Ned replied. "Have you been keeping a good lookout onthe lake since you left it?" he added, turning to Pat.

  "Some one of us has had eyes on it every minute," was the satisfactoryreply. "No one has returned, I'm sure."

  "You're not thinking of going there to-night, are you?" asked Jack, witha slight shiver. "I wouldn't go in there again, even in broad daylight,for a million dollars!"

  "Pat is afraid of the sky, and Jack is afraid of the bowels of theearth!" laughed Frank. "We'll have to tuck them both in bed before wecan accomplish anything."

  "You may all go to bed but one," Ned said, looking about the group, hiseyes finally resting with a significant look on Frank's excited face. "Iwant to look through that cavern before anything is taken out of it."

  Frank, knowing the meaning of the look he had received, went to hislittle tent for his revolver and his electric searchlight and was soonready for the expedition. Jimmie looked sulky for a moment at being leftout of the game, then his face brightened and he crawled into the tentthat had been prepared for Nestor and himself and burst into a fit oflaughter.

  "I'll show 'em!" he said, stuffing the blanket into his mouth tosuppress the sound of his merriment. "I'll teach 'em to put me in thediscard."

  "Any wild animals up here?" asked Ned, as the two started away down thesteep declivity.

  "Two Black Bears and three Wolves!" called Jimmie, from his tent.

  This was a reference to the Boy Scout Patrols to which the boysbelonged. Frank and Jack were members of the famous Black Bear Patrol ofNew York City, while Ned, Pat and Jimmie were members of the WolfPatrol.

  As the lad spoke Frank and Jack broke into growls which might well havecome from the throat of the grizzliest grizzly in the Rocky Mountains,while Pat sent forth a wolf howl, which might well have been a signal tothe pack.

  "You may meet the real thing out here," warned Ned, turning back to lookover the plateau, now shining in the light of a half-moon. "There areboth bears and wolves in this region. When you meet them, don't wait forBoy Scout signs!"

  "Oh, we'll initiate 'em, all right," Jimmie called from the tent, andNed and Frank moved on down the declivity toward the lake.

  It was still early evening, and the moon was low down in the east, sothe valley where the lake lay was not touched by its light. Indeed, theplateau where the boys were would have been in the shadow of themountain only for the dropping of the shoulder of the divide.

  In half an hour the two boys, after several slides which were anythingbut pleasant, gained the beach. The campfire was now dead, and thelocality was still save for the voice of a night bird and the occasionalsplash of a leaping fish. The mouth of the cavern loomed like a darkpatch on the lower bulk of the mountain.

  Making as little noise as possible, Ned and Frank crept into the cavern,advancing by the sense of feeling until they came to the very end beforeturning on one of the electric flashlights. The round eye of the flameshowed a long, narrow, tunnel-like tube running directly east, under themountain. The door of rock was as the boys had left it earlier in theday.

  Ned examined that portion of the rock which had swung out into the firstchamber with considerable care, as the story of the swinging stone hadinterested him greatly. All along the top, up to the center, he foundthe checks of a stone-chisel. Exactly in the middle an elevation of aninch fitted into a round cavity in the upper rock. At the bottom thesame conditions were discovered.

  "Rather a clever job," Ned said, "but I don't see how it was ever done."

  "This door," Frank said, "is not exactly like the remainder of the wallin grain, so it must have been brought here from some other locality. Ofcourse there was a hole between these two chambers, or the second onewould never have been found. It would be easy enough to fit the stonedoor in by grooving out from the lower cavity and sliding the underpivot in."

  "Sure," Ned replied, getting down to examine the lower part of the doormore closely, "and that is just what was done. Then the groove wasfilled with concrete. Pretty classy work here!"

  "And now the question is this," Frank went on, "what was the door fittedfor? Why did the men who found the cave desire privacy? Is there gold inthere? Have the men who have been setting fire to the forestsestablished a home here? Is this the hiding place of a band of outlaws?You see there are lots of questions to ask about the two caverns," Frankadded, with an uneasy laugh.

  Ned closed the stone door and turned on both electric flashlights,making the place light as day where they stood. The inner cavern was asbare as the outer one save for dead leaves and grass which lay in heapson the stone floor, and for half a dozen rough benches which were piledin one corner. At the farther end hung a gaudy curtain, once handsome,but now sadly spotted with mildew because of dampness.

  "Here's the inner chamber," laughed Frank, drawing the curtain aside."And it looks like it was the private office of the bunch, too," headded, as he turned the light about the walls.

  There was a desk in the third cavern, a swivel chair, a small case ofbooks, and a rusty safe, which looked as though it had not been openedfor years. A current of fresh air came from the rear, and a smallopening was soon discovered.

  "That doubtless leads to some canyon not far away," Ned said. "Makes apretty decent place of it, eh?"

  "Good enough for any person to hide in," replied Frank. "Now," he added,"tell me what you think of it. Who cut this cavern, and who brought thefurniture here? I'll admit that my thinker is not working."

  "Nature made the caverns," Ned replied. "There is what geologists call afault in the rock here. Owing to volcanic action, doubtless, the stratashifted, probably thousands of years ago, and when the seam appeared thebroken pieces fell apart. These chambers show the width of the seam.There undoubtedly was a great earthquake at the time, and the lake belowmight have been dredged out at that time."

  "Of course,"
Frank said, "I might have known that! Now, here's anotherquestion: How far does this seam extend under the Rocky Mountains? If itpasses beyond these three chambers, why not make a fourth room forourselves so as to be on the spot when the men who make headquarters ofthe place come back?"

  "That may be a good thing to do," Ned admitted, "but, still, I would notlike to be the one to lie in wait here. Suppose we try to learnsomething of the character of the people who come here? They seem tosleep on dry leaves and eat off benches. Rather tough bunch, I take it.Perhaps we have struck Uncle Sam's enemies the first thing!"

  Keeping their lights on, and working as silently as possible, alwayswith an eye to the outer cavern, the boys made a careful search of theinner chamber. The desk was not fastened, and a cupboard afterwarddiscovered in a niche was open also. There were dishes in the cupboardand writing materials in the desk.

  At the very bottom of the desk drawer Ned came upon a surprise.

  "Not so tough as I supposed," he said, turning to Frank. "Here's atypewriter ribbon. The sort of people who set fire to forests and holdup trains are hardly in the typewriter class. What do you make of it?"

  "Well," Frank said, with a chuckle, "if you'll tell me what theinhabitants of this place want of typewriter ribbons I'll tell you whythey bring great tins of opium here. It seems that we have strucksomething more important than forest fires."