CHAPTER II.--THE SIGNAL IN THE SKY.
Frank left the cavern in a moment and walked along the beach toward thecampfire. His thought was to gather embers and fresh fuel and build up ablaze at the end of the cave which would reveal every inch of theinterior. He was certain that Jack had not left the place, and decidedthat he had fallen into some hidden opening which had escaped his owninvestigation.
As he bent over the remains of the fire he heard a rattle of smallstones, and, looking up, saw Pat coming down the declivity from theplateau where the tents had been set up. The incline was steep, and attimes Pat was rolling rather than walking. He was in his shirt sleevesand bareheaded. At last his red head pitched toward the lake like ameteor in downward flight.
Frank rushed forward and caught him as he struck the beach, thus savinghim from an impromptu bath. Pat struggled to his feet in an instant,rubbed his legs and arms to see if any bones had been broken, and thenturned his head and looked up the incline.
"Talk about shooting the chutes!" he exclaimed. "I wonder what time Imade coming down?"
"Sure you're not hurt?" asked Frank anxiously.
"Every inch of my body has three bruises, one on top of the other," Patreplied, "but I guess I'm able to walk. Say, but that was aroller-coaster glide!"
"Why did you try such a foolish caper?" asked Frank.
"Why, I saw you boys here," was the reply, "and started down. You knowthe rest, as the yellow-covered books say. What you boys doing here,wasting your time, with the bacon burning to a crisp?"
"We came here to investigate," was the reply, "and Jack went into thecavern, and vanished--just vapored into thin air. I'm going to build afire in there and see if I can't condense him!"
"Well," Pat said, listening, "he may have vanished physically, but hisvoice appears to be on deck yet."
Three sharp calls came from the cavern, and both boys dashed inside.There was no doubt now that Jack's voice, at least, had condensed, forthe shouts coming from the back of the cavern were both hearty andimperative.
"Hi, there!" Jack called. "Pry this stone out of the doorway!"
"Where are you?" demanded Pat. "Which one of the walls do you want us topush in? You're a nice chump, getting in a scrape like this!" he added,with a laugh which must have been exasperating to the unseen boy.
"You'll find a crevice where the back of the cave joins the south wall,"Jack said, his voice coming faintly to the ears of his chums. "Put yourfingers in and pull. The blooming door opens outward. Hurry! It'sstifling in here!"
After burning nearly all the matches they had in their pockets, andscorching their fingers on the short sticks, Pat and Frank discoveredthe crevice spoken of and inserted the ends of their fingers.
"Pull!" yelled Jack. "Pull, you loafers! It is moving!"
In a moment the south half of the back wall swung out so suddenly thatboth boys were thrown from their feet and Jack, who had been pushingwith his whole strength, came tumbling on top of them as they lay on thefloor of the cavern.
"What sort of a combination is this, anyway?" demanded Pat, strugglingto his feet. "If I get any more bumps to-day I'll be taking somethingthat belongs to some one else. I've had my share."
Frank sprang to the opening as soon as he could disentangle himself fromthe collection of arms and legs and looked in. All was dark and stillinside, and a gust of dead air struck him in the face. Pat, leaning overhis shoulder, laid a hand on the rock which had opened so strangely, andthe next instant it closed softly, sliding into the opening like a dooroperated by well-oiled machinery.
"Now you've done it!" Frank exclaimed, disgustedly, as Pat threw himselfagainst the stone in a vain effort to force it open again.
"No harm done," Jack exclaimed. "There's only a stinking cavern inthere. Wow! I can feel snakes and lizzards crawling on me now! Come! Letus get into the open air. Stifles like a grave in here."
The boys hastened outside and stood meditatively before the shiningwaters of the lake, each one trying to think clearly concerning what hadtaken place. They believed themselves--or had believed, rather--milesaway from any trace of civilization, and yet here was a practical doorof rock at the end of a cave almost under the great divide.
"We've found something," Frank said, at length. "That thing in therenever happened. Human hands fashioned that door for some secret purpose.And it wasn't Indians, either."
"I guess we've run up against a band of train robbers," suggested Jack,with a grin.
"Probably the entrance to some deserted mine," Pat put in. "This regionhas been searched for gold for fifty years. I've heard of mines beingconcealed by moving stones."
"Well," Frank said, after a short silence, during which all listened forsome indication of the immediate presence of the men who had been seento row around the green point a short time before, "whatever the gameis, we've got to remove every trace of our visit. When they come backthey probably won't notice the tracks we have made, for there wereplenty about before we came here, but we must gather up all thematch-ends we left in there and leave the door as we found it."
"I found it open and walked in," Jack said, "and then it closed. Whew! Ifelt like I was being shut up in a tomb!"
"How large a place is it in there?" asked Pat.
"Don't know," was the reply. "I had no matches with me, and so could notsee a thing."
"Then we won't have to open the door again to clean up any muss," Franksaid, moving toward the entrance to the cavern.
"I wouldn't go in again for a thousand dollars," Jack cried. "If youleave it to me, the place is haunted. I heard groans in there."
Frank paused at the entrance and turned back. His matches were aboutgone, and so he took a burning stick from the fire, added two dryfaggots to it, waited until the three burst into flame, and then enteredthe cave.
To gather up the half-burned matches which had been scattered over thefloor was the work of only a moment.
"Now you'll have to open the door, if you leave it as I found it," Jacksaid, looking in from the mouth. "Pat will help you."
"Come on in, both of you," Frank directed.
"Not me!" cried Jack. "I hear bones rattling!"
The boys thought he was joking at first, but it soon appeared that hewas in sober earnest, so Pat and Frank, by exerting their entirestrength, managed to open the door without his assistance.
"You're afraid of the dark!" Pat taunted, as the boys gathered aroundthe fire again.
"I'm not half as afraid of the dark as you are of an aeroplane," Jackreplied. "If I ever see you going up in a 'plane, I'll go in therealone."
"Don't you ever forget that," Pat grinned.
"Oh, I'll be game, all right," was the reply.
Before leaving the beach for the camp the boys walked to the pointaround which the boat had gone and scanned the lake and its shoresthrough the field-glass. There was no sign of life anywhere, exceptwhere the birds swung from forest limbs back from the rim of the lakeand called each other through the sultry air.
Reaching the camp after a weary climb, they did full justice to the mealwhich Pat had prepared, though the bacon and the hoecakes were stonecold, or at least as cold as anything could be in that glare ofsunlight. Then, the dishes washed and the beds prepared for the night,they sat down to watch the lake and the sky to the south, for it was nowthe general belief that Ned would make his appearance with the aeroplanewhich had been promised by the government officials.
The point they had last visited, as well as the location of the fire,was in full view of the plateau, so the boys made no efforts to concealtheir presence there. The men who had been observed in the boat musthave noted their presence on the plateau before taking their leave.Perhaps, they reasoned, they had taken their departure because of thisinvasion.
The sun sank lower and lower in the sky, turning the plateau and thesmooth waters of the lake to gold, still there were no signs of Ned, noindications of the return of the boat to the place from which it hadbeen launched. Half an hour after dark, Frank, who
was looking throughthe field-glass, caught sight of light in the south which did not appearto come from any star.
"Here he comes!" he cried. "That's an aeroplane, all right!"
As the light drew nearer, traveling rapidly, the sharp explosions of thegasoline engine became audible. Then a light flickered over the upperplane, passed off, and swept the white surface again.
"How does he make that?" demanded Pat. "Looks like a great questionmark."
"That's what it is," Frank exclaimed. "Now, what does he mean by it?"