CHAPTER XXVI
THE SECRET TUNNEL IN THE MESA
At five o'clock Ned and Alan were astir. With regrets that theywere not at Camp Eagle for a plunge in the cool mountain lake, theyprepared another hot meal, ate it, and boarded the Cibola.
The balloon had now been inflated thirty-eight hours and wasnoticeably showing the loss of its gas. While the top of the bagwas yet round and firm in the heat of the sun the lower sides hadbecome a trifle flabby as the cool evening had come on. Up to thistime all records for balloon flight had been broken a fact due tothe renewed buoyancy caused each day by the hot, Southwestern Sun.And, exploration in and quick ascent from the canyons before themwould before long call for the use of ballast. The boys agreed thatthe time had arrived to utilize their liquid hydrogen. Theshrinkage that night had been quite perceptible.
They regretted that but two-thirds of this remained--about elevencubic feet. This when reconverted meant nearly twelve thousandcubic feet of new gas at their present altitude. As the work ofconverting the gas involved care, preparation for it was made beforethe Cibola was cut loose.
The reconverter, a reduced inversion of the apparatus used in makingliquid air, was made ready. When the muffled explosions and theheat of the tubes told the boys that the reconverter was workingperfectly and pumping new and needed gas into the shrunken Cibola'slong bag, the lashings were loosed and once more the faithfuldirigible mounted skyward.
With Major Honeywell's map of the region spread out on the deck ofthe bridge and the binoculars in hand Ned began the long anticipatedsearch for the lost city.
All day the process of turning the liquid hydrogen back into buoyantgas went on. And all day the Cibola wound her devious course overthe peaks and chasms beneath. By night half the hydrogen jars wereempty and Ned and Alan saw the evening close in on them without asign of the object of their search. When darkness stopped furtherwork the balloon was brought to earth and camp made again.
The following day, as uneventful as the first, gave no indication ofthe secret city. The rest of the liquid hydrogen was transformedinto gas. The sun seemed to enfold the craft in a fiery embrace.When camp was made again that night the Cibola had been afloateighty hours.
"I think she is good for another forty-eight hours," said Ned thatnight. "If we find nothing in two more days we'll have our choiceof going out on foot or of quitting in time to pick up Elmer and Boband make a dash to civilization. What do you say?"
"I don't know," replied Alan, "I'd hate to give up as long as we canfly. I think the boys can care for themselves. Let's stick to it.We have provisions and there is water in some places."
"Well," answered Ned, "we'll have two more days time in which todecide."
The next morning the Cibola showed plainly that her gas was rapidlyescaping. New life was given to the balloon by casting overboardsome empty hydrogen casks. The fourth day broke hotter than ever.In all the wilderness examined by the tired and strained eyes of thesearchers, not a human being had been seen--not even a wanderingNavajo. This day they began the search with renewed vigor, but withthe same monotonous result--miles of hopelessly desert rock and sandbeneath them, with a little vegetation now and then, but so sign ofIndian remains.
At noon Ned said:
"If we were not in a balloon with a compass and sextant I should saywe were lost. And if Indians ever lived and died hereabouts theycertainly left so signs of their bones."
By six O'clock, with the sun gratefully low, Alan expresseddiscouragement.
"To-morrow at this time," he said, "if we see no indication of theold palace or city or whatever it was--if it ever was--I think I'llvote to try to find Camp Eagle and get out."
"We'll see to-morrow," answered Ned stoutly.
That night at dark, a landing was made on the ledge of a point ofland ending in a rounded cliff pointing south, selected because theplace was open to the breeze and cool. The Cibola had approachedthe height from the west, and the boys believed that the promontoryprojected from yet higher ground beyond. On those portions of thecliff that they could see there was neither shelf nor projection ofany kind. The walls rose almost like cut stone and were apparentlyabout three hundred feet high. As the Cibola was about to descend,Alan, who was taking a last survey from the bridge, called Ned'sattention to the fact that even the far side of the supposedpromontory was separated from the mountains beyond, and that a chasmat least a half mile wide separated the two heights.
"It's a mesa," replied Ned with renewed enthusiasm, "and it will bea good thing to look over it to-morrow. These high and almostunapproachable islands of rock were favorite dwelling places for theIndians."
"But a temple up here wouldn't be a secret very long," replied Alan."We've seen this point all afternoon. It's prominent enough."
"That's so," answered Ned, "but we are here, so let's make a landingand eat, and dream over it."
The balloon had now lost so much gas that a landing was easy, and,tired with four days' profitless search and its strain, the youngaeronauts were soon beyond even dreams.
It was with no small alarm that the boys saw, when they awoke withthe first rays of the sun, that the car of the Cibola, which hadbeen anchored fore and aft to heaped up rocks during the night, wasnow resting on the ground. Gas, was rapidly escaping. But fortunatelythe aeroplanes and propeller had been left properly in a horizontalposition and no damage had been done.
The boys knew that by throwing over enough ballast and stores theCibola could be made good for one more flight, but that probably itwould be the last. Therefore, the inevitable seemed forced uponthem. They would fortify themselves with a good breakfast, lookover the mesa, make one more circling flight and then attempt tofind Camp Eagle. While Alan made haste to prepare breakfast, Neddetermined first on an examination of the mesa point by daylight.
The rock had a top area of perhaps forty or fifty acres. It had arolling surface and was coated with a carpet of dusty sand, exceptin the northwest corner. The northern end of the mesa, Ned couldsee, widened and ended in a sharp rise almost wall-like in form. Atthe western end this wall-like elevation turned the corner andextended south a short distance, finally dropping down to thegeneral level of the mesa. In this protected comer grew a strangegrove of gnarled and twisted pines, ill nourished and apparentlyvery old. Between this comer of the mesa and the sharper promontorywhereon the Cibola had come to anchor, was a wide, sandy, barrendepression.
The narrow portion of the rocky island where the boys had made campdrew in abruptly to make the point that marked the southern end ofthe mesa. Ned turned first toward the point.
When he had advanced, making his way slightly upward all the time,to where the narrow mesa was not over four hundred feet wide, thelad was astounded to suddenly discover a deep and narrow fissure orchasm. It was dark, with sides as abrupt as the cliffs of the mesa,and too wide to jump across. A cold air was already rising from theopening into the warmer atmosphere above.
In his astonishment Ned called to his chum.
"What surprises me," exclaimed Ned, "is the character of theopening. If it extended from cliff to cliff I should say that thesame freak of nature that made this solitary island of rock alsosplit off this end at some time. But it is closed at each end."
Alan hastened to the end of the fissure, near the side of the mesa.
"It looks to me," he said, "as if it had extended entirely across atsome time and the ends walled up later."
The boys made a closer examination.
"You're right," said Ned when he discovered that each end of therift had been filled with closely fitted rock, "and human hands didit."
Alan sprang up in excitement.
"That's the first sign we've had," he exclaimed. "Do you suppose itmeans anything?"
The edge of the cliff was so abrupt that the boys had to lie down tolook over in safety.
"It does," Ned answered. "The reason you can't see that chasm frombelow or from in front is because the face of it is w
alled up. Andit is walled so skillfully that you can't detect it from even ashort distance."
"That's to hide something," quickly replied Alan, "but I don't see--"
Ned was standing on top of the short filled-in portion of the chasm.
"Look!" he exclaimed, suddenly interrupting his friend. "Thesestones are steps, and, they are worn!"