THE SECRET TUNNEL IN THE MESA
At five o'clock Ned and Alan were astir. With regrets that they
were not at Camp Eagle for a plunge in the cool mountain lake, they
prepared another hot meal, ate it, and boarded the Cibola.
The balloon had now been inflated thirty-eight hours and was
noticeably showing the loss of its gas. While the top of the bag
was yet round and firm in the heat of the sun the lower sides had
become a trifle flabby as the cool evening had come on. Up to this
time all records for balloon flight had been broken a fact due to
the renewed buoyancy caused each day by the hot, Southwestern Sun.
And, exploration in and quick ascent from the canyons before them
would before long call for the use of ballast. The boys agreed that
the time had arrived to utilize their liquid hydrogen. The
shrinkage that night had been quite perceptible.
They regretted that but two-thirds of this remained--about eleven
cubic feet. This when reconverted meant nearly twelve thousand
cubic feet of new gas at their present altitude. As the work of
converting the gas involved care, preparation for it was made before
the Cibola was cut loose.
The reconverter, a reduced inversion of the apparatus used in making
liquid air, was made ready. When the muffled explosions and the
heat of the tubes told the boys that the reconverter was working
perfectly and pumping new and needed gas into the shrunken Cibola's
long bag, the lashings were loosed and once more the faithful
dirigible mounted skyward.
With Major Honeywell's map of the region spread out on the deck of
the bridge and the binoculars in hand Ned began the long anticipated
search for the lost city.
All day the process of turning the liquid hydrogen back into buoyant
gas went on. And all day the Cibola wound her devious course over
the peaks and chasms beneath. By night half the hydrogen jars were
empty and Ned and Alan saw the evening close in on them without a
sign of the object of their search. When darkness stopped further
work the balloon was brought to earth and camp made again.
The following day, as uneventful as the first, gave no indication of
the secret city. The rest of the liquid hydrogen was transformed
into gas. The sun seemed to enfold the craft in a fiery embrace.
When camp was made again that night the Cibola had been afloat
eighty hours.
"I think she is good for another forty-eight hours," said Ned that
night. "If we find nothing in two more days we'll have our choice
of going out on foot or of quitting in time to pick up Elmer and Bob
and 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 can
fly. 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 to
decide."
The next morning the Cibola showed plainly that her gas was rapidly
escaping. New life was given to the balloon by casting overboard
some empty hydrogen casks. The fourth day broke hotter than ever.
In all the wilderness examined by the tired and strained eyes of the
searchers, not a human being had been seen--not even a wandering
Navajo. This day they began the search with renewed vigor, but with
the same monotonous result--miles of hopelessly desert rock and sand
beneath them, with a little vegetation now and then, but so sign of
Indian remains.
At noon Ned said:
"If we were not in a balloon with a compass and sextant I should say
we were lost. And if Indians ever lived and died hereabouts they
certainly left so signs of their bones."
By six O'clock, with the sun gratefully low, Alan expressed
discouragement.
"To-morrow at this time," he said, "if we see no indication of the
old palace or city or whatever it was--if it ever was--I think I'll
vote 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 of
land ending in a rounded cliff pointing south, selected because the
place was open to the breeze and cool. The Cibola had approached
the height from the west, and the boys believed that the promontory
projected from yet higher ground beyond. On those portions of the
cliff that they could see there was neither shelf nor projection of
any kind. The walls rose almost like cut stone and were apparently
about three hundred feet high. As the Cibola was about to descend,
Alan, who was taking a last survey from the bridge, called Ned's
attention to the fact that even the far side of the supposed
promontory was separated from the mountains beyond, and that a chasm
at least a half mile wide separated the two heights.
"It's a mesa," replied Ned with renewed enthusiasm, "and it will be
a good thing to look over it to-morrow. These high and almost
unapproachable islands of rock were favorite dwelling places for the
Indians."
"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 landing
and 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 young
aeronauts were soon beyond even dreams.
It was with no small alarm that the boys saw, when they awoke with
the first rays of the sun, that the car of the Cibola, which had
been anchored fore and aft to heaped up rocks during the night, was
now resting on the ground. Gas, was rapidly escaping. But fortunately
the aeroplanes and propeller had been left properly in a horizontal
position and no damage had been done.
The boys knew that by throwing over enough ballast and stores the
Cibola could be made good for one more flight, but that probably it
would be the last. Therefore, the inevitable seemed forced upon
them. They would fortify themselves with a good breakfast, look
over the mesa, make one more circling flight and then attempt to
find Camp Eagle. While Alan made haste to prepare breakfast, Ned
determined first on an examination of the mesa point by daylight.
The rock had a top area of perhaps forty or fifty acres. It had a
rolling surface and was coated with a carpet of dusty sand, except
in the northwest corner. The northern end of the mesa, Ned could
see, widened and ended in a sharp rise almost wall-like in form. At
the western end this wall-like elevation turned the corner and
extended south a short distance, finally dropping down to the
general level of the mesa. In this protected comer grew a strange
grove of gnarled and twisted pines, ill nourished and apparently
very old. Between this comer of the mesa and the sharper promontory
whereon the Cibola had come to anchor, was a wide, sandy, barren
depression.
The narrow portion of the rocky island where the boys had made camp
drew in abruptly to make the point that marked the southern end of
the 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, the
lad was astounded to suddenly discover a deep and narrow fissure or
chasm. 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 the
opening into the warmer atmosphere above.
In his astonishment Ned called to his chum.
"What surprises me," exclaimed Ned, "is the character of the
opening. If it extended from cliff to cliff I should say that the
same freak of nature that made this solitary island of rock also
split 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 at
some 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 the
rift had been filled with closely fitted rock, "and human hands did
it."
Alan sprang up in excitement.
"That's the first sign we've had," he exclaimed. "Do you suppose it
means anything?"
The edge of the cliff was so abrupt that the boys had to lie down to
look over in safety.
"It does," Ned answered. "The reason you can't see that chasm from
below or from in front is because the face of it is walled up. And
it is walled so skillfully that you can't detect it from even a
short 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. "These
stones are steps, and, they are worn!"