"and now," said alan, "it's ho, for camp eagle and our search at last."

"i don't know about all that sentiment," answered ned, thoughtfully. "i've been—"

but he was interrupted. the boys, aboard the cibola again, were just about to cast off when alan cut short ned's remark with an exclamation.

"isn't that a balloon?" he exclaimed pointing to an orange-like object high in the heavens toward the west.

ned caught up the binoculars and had a quick look at the rapidly moving ball which was rushing toward them from over the distant tunit chas mountains.

"no question about it," answered ned, handing alan the glasses; "a balloon, and a big one."

"and out here, too!" commented alan in surprise. "i guess the world is pretty small after all."

"everything ready?" asked ned eagerly. and then as the retaining rope was untied from the frame of the car and slipped down and out from under the cottonwood snag the cibola shot upward.

"i have an idea," continued ned, "and please don't object until you think it over. let's make a little social call on the stranger!"

"a call!" exclaimed alan, plainly showing his astonishment; "a call on a balloon five thousand feet in the air?"

"certainly. we are going that high anyway. and we have the means of going where we like. if we go up until we strike the same, stratum of air the stranger is moving in we have our propeller and aeroplanes to check and guide ourselves. when it passes we can easily run alongside!"

"well, if that isn't the limit!" laughed alan. "and i suppose we'll exchange greetings and messages like ships long at sea."

"and," added ned, "we can send some word to major honeywell. you can see our fast flying friend isn't going to stop around here."

the cibola was rising fast and the two air craft were coming closer and closer. as the dirigible reached the altitude at which the free balloon was sailing ned put the aeroplane in operation, stopped the ascent of the cibola and then, sweeping his own car into the same direction with the other balloon he reversed the propeller and held his own craft against the breeze until the stranger swept by.

then, throwing on the propeller again at full speed, ned made the cibola bound after the other craft, and in a few minutes, aided by the favoring wind, they were within hailing distance.

ned was on the bridge, his face flushed with the novelty of the race. a mile above the earth, the two air ships came closer until, as if running on parallel tracks, they were nearly together and abreast.

"balloon ahoy!" exclaimed ned at last and in true maritime style.

"the arrow of los angeles, bound across the continent," came the sharp answer.

"the cibola from clarkeville, new mexico," called ned in reply, "exploring. please report us over mount wilson."

then the two ships of the sky came closer. the boys could see that the arrow was well equipped for its purpose. two determined looking aeronauts were leaning from the heavily laden car.

"need anything?" shouted the arrow cordially.

"in good shape," answered ned, "but a little short on provisions."

"plenty here," came quickly from the arrow, "glad to exchange fifty-pound emergency rations for ballast."

"all right," responded ned, "stand by to make a line fast."

alan, at the engine, brought the air ship up as skillfully as a pilot might a vessel, and as the two cars almost touched ned passed the end of his drag rope, and the occupants of the arrow with a quick turn made her basket fast to the bridge of the cibola. there were handshakes, mutual congratulations and quick explanations. the arrow, the property of a wealthy amateur balloonist, was attempting to sail, from the pacific to the atlantic and was, so far, beating the best calculation of her owner. in reaching the desired height that morning, however, much ballast had been used and the possibility of a renewed supply was jumped at.

"these extra provisions were packed with the idea of possibly using them as ballast and we don't really need them. and, so," they explained to the boys, "if you do you had better take them and give us sand."

the exchange was quickly made, and then, having stored their new food supply safely on the bridge, they said hasty farewells.

ned had scribbled this note on a page from his note book: "major baldwin honeywell, annex, chicago. by courtesy of balloon arrow. bourke, escort, killed by indians. search begins at once. camp established on plateau, second range tunit chas mountains, thirty miles due east wilson's peak. greetings. written 5,600 feet above san juan river, new mexico. ned napier and alan hope."

the case of provisions weighed a trifle more than the ballast given in exchange, and as the line holding the two cars together was cast off the cibola sank slowly below the level of the arrow. then, as the cibola's engines began to push the car ahead in a wide turning circle, ned called up to the disappearing arrow:

"great country, this new mexico, where you can buy food with sand. good-bye and success to you!"

the answer was lost in space as the ships parted.

"and now," said ned, after lashing the now case of provisions to the bridge netting, "we've wasted some more precious time. do you still think we had better lose a night at camp eagle? we have all the fuel we can carry."

alan saw what was in the wind.

"we have extra provisions, water and gasoline. my own judgment is we had better make at once for our starting point."

"i guess you are right," answered alan after long thought; "i don't know what is to be gained by the trouble of a landing at the camp by the lake."

"nothing but that hot supper," smiled ned, "and we'll have to put that off a few days, i think."

"all right," agreed alan, "set your course and with luck we'll do a little treasure hunting before dark."

this being settled, the prow of the cibola was pointed a little west of northwest, and, dropping to a lower stratum to escape the lively eastern breeze at the higher altitude, the boys started at last directly for the and arid broken mountains of northwestern arizona.

this region, bordering on the great sand dunes lying beyond the chelly river, was to be the beginning point of their arduous and momentous search. from that place to a point nearly one hundred miles to the southeast lay the secret fastnesses of mountain, canyon and mesa wherein, somewhere, according to the spanish soldier's record, was the secret city of a dead race and the treasure that had brought ned and alan half way across a continent.

what such a search meant one glance at the monotonous and unending rock easily told. on foot, only the compass could lead a man forward in such wilderness of abrupt heights and winding chasms. as the boys meant to manage it, the attempt had possibilities, but it might mean days of drifting, of watching, of doubling back and forth over every possible site. and that was now their task.

so far as they could, ned and alan meant to begin at the extreme northern end of this unknown land and, sailing back and forth from east to west, cover every foot of exposed ground with their powerful glasses.

both boys had long since agreed in this conclusion: the "city" meant no more than one large structure similar to but on a larger scale than those found in the chaco canyon at the extreme southern end of the tunit chas mountains. this would be indicated now by nothing more than rectangular lines of wall stones, probably in piles, outlining the shape of the "city" or palace. prominent among these ruins should be the more elevated temple, the object of their search. and beneath this should be found the underground "khivas" or religious chambers.

that this "city" was secret or hidden was proof to ned and alan and major honeywell that it would not occupy a prominent place such as an exposed plateau or a high level mesa. only one other location was left, the abutting shelf of some canyon. and the young navigators had pictured to themselves that, if this should prove to be the location, the shelf would be so elevated as not to be visible from the front or below and that it would be concealed from above by an extended and overhanging cliff.

"look for it as you would look for a bird's nest in the cliff," suggested ned. and that was the plan of search.

it was nearly three o'clock when the boys had bade farewell to the arrow and about half past five when the cibola sailed over the second ridge of the tunit chas. but the course was far to the north and there was naturally no sign of the waterfall plateau or camp eagle. for a time they thought of passing over the camp and dropping a message, but this pleasant idea was given up.

"although," as alan expressed it, "one of elmer's hot suppers and a soft bed of balsam boughs to-night wouldn't be bad."

ned thought of the four nights of hard floor and agreed, but he said:

"you'll have to forget soft beds if we're ever going to find cibola. we'll come down to-night, though, and make a camp of our own with a fire and a pot of coffee, and at daybreak we'll be off."

the boys had taken a light luncheon just after starting on the return trip, and now, soaring over the tunit chas again, they began to be anxious for night and supper.

at seven o'clock the peaks and ridges below them had begun to drop into foothills and as the great sandy deserts of distant utah and nearer by arizona came before their eyes the boys decided that it was time to anchor for the night. they were sailing over the eastern slope of the last low ranges of hills, barren of trees or vegetation. the aeroplanes being given the proper depression, the cibola shot earthward and then, the propeller coming to a pause, floated gently along above the jumble of rocks. making fast the anchor in a ragged pile of these the boys soon drew the cibola to the ground and lashed her fore and aft to heavy boulders.

the firm ground felt delicious to the tired boys and they refreshed themselves with a brisk race over the open space between the rock piles. then came alan's camp fire, a hot supper and preparations for a good night's rest. there were no pine needles of balsam boughs, but fatigue made a fine mattress, and it was not long before the tired boys, rolled up in their blankets, were fast asleep on the soft sand.

"i hope," said ned drowsily as they were dropping off to sleep, "that we won't have any jack jellups or thieving utes to-night. my nerves need rest."

then the boys got eight good hours of health and strength giving sleep in the tonic air of the arizona mountains.