In place of the indulgent smile for which he was playing, Waldo received a frown, and directly thereafter the professor spoke in tones which could by no possibility be mistaken.

“Come with me, both of you. I am going back to the aerostat, and I dare not leave you boys behind. Come!”

Kind of heart and generally complaisant though uncle Phaeton was, neither Bruno nor Waldo cared to cross his will when made known in such tones, and without further remonstrance they followed his lead, slipping away from the snug little observatory without drawing attention to themselves from any of yonder busy horde.

Not until the trio was fairly within the gulch did the professor speak again, and then but a brief sentence or two.

“Give me time to weigh the matter, lads. Possibly I may agree, but don't try to hurry my cooler judgment, please.”

Waldo gave his brother an eager nudge at this, gestures and grimaces being made to supply the lack of words. But when, the better to express his confidence that all was coming their way, the youngster attempted a caper of delight, his foot slipped from a leaf-hidden stone, and he took an awkward tumble at full length.

“Never touched me!” he cried, scrambling to his feet ere a hand could come to his aid. “Who says I don't know how to stand on both ends at the same time?”

Barring this little caper, naught took place on their way to the air-ship; and once there, the professor heaved a mighty sigh, wiping his heated face as one might who has just won a worthy race. But he betrayed no especial haste in setting the flying-machine afloat and Waldo finally ventured:

“Can we help you off, uncle Phaeton?”

But he was assured there existed no necessity for such great haste.

“In fact, it might be dangerous to start while so many of the Aztecs are upon the lookout,” came the unexpected addition. “I believe it would be vastly better not to leave here until shortly before dawn, to-morrow.”

It took but a few words further to convince the brothers that this idea was wisest, and while the young fellows felt sorry to have their view cut so short, neither ventured to actually rebel.

After all, the day was well-nigh spent, and, besides preparing their evening meal, it was essential that their plans for the immediate future should be shaped as thoroughly as possible.

Professor Featherwit had resolved to fetch Cooper Edgecombe to the scene of interest, in order to give him at least a fair chance to solve the enigma which was perplexing them all. Even so, he felt that no small degree of physical danger would attend that presence, particularly if it should really prove, as they could but suspect, that both wife and daughter of the involuntary exile were yonder, among the Aztecans.

Much of this the professor made known to his nephews during that evening, the trio thoroughly discussing the matter in all its bearings, but before the air-ship was prepared for the night's rest, uncle Phaeton made the youngsters happy by consenting to their remaining behind as guardians to the Lost City, while he went in quest of the balloonist.

“But bear ever in mind the conditions, lads,” was his earnest conclusion. “I place you upon your honour to take all possible precautions against being discovered, or even running the least unnecessary risk during my absence.”

“Don't let that bother you, uncle Phaeton,” Waldo hastened to give assurance. “We'll be wise as pigeons, and cautious as any old snake you ever caught up a tree; eh, Bruno, old man?”

“We promise all you ask, uncle, but does that mean we must stay right here, without even stealing a weenty peep at the Lost City?”

Professor Featherwit felt sorely tempted to say yes, but then, knowing boyish nature (although Bruno had just passed his majority, while Waldo was “turned seventeen”) so well, he feared to draw the reins too tightly lest they give way entirely.

“No; I do not expect quite that much, my lads; but I do count on your taking no unnecessary risks, and in case of discovery that you rather trust to flight, and my finding you later on, than to actually fighting.”

So it was decided, and at a fairly early hour the trio lay down to sleep. Although so unusually excited by the marvellous discoveries of the day just spent, their open-air life tended to calm their brains, and, far sooner than might have been expected, sleep crept over them, one and all, lasting until nearly dawn.

Perhaps it was just as well that the wakening was not more early, for the professor was beginning to regret his weakness of the past evening, and had there been more time for drawing lugubrious pictures of probable mishaps, he might even yet have insisted on taking the youngsters with him.

Knowing that it was rather more than probable some of the Indians would be stationed upon the hills to watch for the queerly shaped air-demon, the professor felt obliged to lose no further time, and so the separation was effected, just as the eastern sky was beginning to show streaks and veins of a new day.

“Touch and go!” cried Waldo, with a vast inhalation as he watched the aeromotor sail away with the swiftness of a bird on wing. “And for a weenty bit I reckoned 'twas you and me as part of the go, too!”

In company the lads enjoyed a more leisurely meal than their relative had dared wait for, knowing that, at the very least, they would have the whole of that day to themselves, so far as uncle Phaeton was concerned. As a matter of course, he would not attempt to return except under cover of night, or in the early dawn of another day.

All that had been thoroughly discussed and provided for the evening before, and was barely touched upon by the brothers now. Their first and most natural thought was of yonder Lost City, with its inhabitants, red, white, and yellow, as Waldo put it; but being still under the foreboding fears of the professor, they finally agreed to remain where he left them until after the sun crossed its meridian.

It was a rather early meal which the brothers prepared, if the whole truth must be told; and the last fragments were bolted rather than chewed, feet keeping time with jaws, as they hastened towards the observatory.

There was pretty much the same sort of view as on the day before, the main difference being that many of the Indians were labouring in the fields, instead of watching for the air-demon.

Using the glass by turns, the lads kept eager watch for the white women whom Waldo stubbornly persisted were within the town; but hour after hour passed without the desired reward, and Bruno began to doubt whether there was any such vision to be won.

“The sun was in your eyes, and you let mad fancy run away with your better judgment, boy,” he decided, at length. “If not, why—what now?”

For Waldo gave a low, eager exclamation, gripping the field-glass as though he would crush in the reinforced leather case. A few moments thus, then he laughed in almost fierce glee, thrusting the glass towards his brother, speaking excitedly:

“A crazy fool lunatic, am I? Well, now, you just take a squint at the old house for yourself and see if—biting you, now, is it?”

For Bruno showed even more intense interest as he caught the right line, there taking note of—yes, they surely were white women! Faces, hair, all went to proclaim that fact. And more than that, even.

“Fair—lovely as a painter's dream!” almost painfully breathed the elder Gillespie. “I never saw such a lovely—”

“Injun squaw, of course. Couple of 'em. Nobody but a fool would ever think different. The idea of finding white women—”

“They are ladies, Waldo! I never saw such—and I feel that they must be the ones lost by poor Edgecombe when that storm—”

“That's all right enough, old fellow,” interrupted Waldo, claiming the glass once more. “No need of your playing the porker on legs, though, as I see. Give another fellow a chance to squint. But aren't they regular jo-dandies, though, for a fact?”

The two women in question, clad in flowing robes of white, lit up here and there by a dash of colour, were slowly pacing to and fro upon the temple where first discovered by the keen-eyed youngster. Thanks to the excellent glass, it was possible to view them clearly in spite of the distance, and there could be no dispute upon that one point: both mother and daughter (granting that such was their relationship) were more than ordinarily fair and comely of both face and person.

For the better part of an hour that slow promenade lasted, and until the women finally passed beyond their range of vision, the brothers took eager and copious notes. Then, in spite of the fact that scores of other figures still came within their field of vision, curiosity lagged.

“It's like watching a street medicine show, after hearing Patti or seeing Irving,” muttered Bruno, drawing back and stretching his wearied limbs beyond possible discovery.

“Or the A B C class playing two-old-cat, after a league game of extra innings; right you are, my hearty!” coincided Waldo, feeling pretty much the same way, “only with a difference.”

Shortly after this, Bruno suggested a retreat to the rendezvous, and for a wonder his brother agreed without amendment.

The brothers passed down to the gulch, which formed the easiest route to their refuge, saying very little, and that in lowered tones. The confirmation so recently won served to stir their hearts deeply, and neither boy could as yet see a way out of the labyrinth that discovery most assuredly opened up before them.

“Of course we can't leave them there to drag on such a wretched existence,” declared Bruno. “We couldn't do that, even though we learned they held no relationship to Mr. Edgecombe. But—how?”

“I reckon it's—what?” abruptly spoke Waldo, gripping an arm and stopping short for a few seconds, but then impulsively springing onward again as wild sounds arose from no great distance.

A score of seconds later they caught sight of a huge grizzly bear in the act of falling upon a slender stripling, whose bronze hue as surely proclaimed one of the Aztec children from yonder Lost City.

What was to be done? Disobey their uncle, or leave this lad to perish?