He picketed the horses, and began ripping open the packs.

Frank turned to Professor Scotch, saying, quietly:

"Bushnell will not go, and I shall stay with him. At the same time, I advise you to go. Take Hans with you, and get away from here. Leave a plain trail, and Bushnell will be able to follow it, if we succeed in reaching the palace and returning alive."

The professor entreated Frank to change his mind, but the lad was determined, and nothing could alter that determination.

At last Scotch gave up in despair, groaning:

"If you stay, I stay. I am your guardian, but you seem to have things all your own way. If this volcano cooks us all, you will be to blame for it."

Frank said no word, but went about the task of a.s.sisting Bushnell in the work of inflating the balloon.

The Westerner had a "gas generator," which he was getting in order. As soon as this was ready, the balloon was unrolled, spread out, drawn up by means of poles and lines, and then secured to the ground by one stout rope, which was. .h.i.tched about the base of a great bowlder.

Then Bushnell built a fire and set the "gas generator" at work.

In the meantime the volcano had continued to mutter. At intervals the clouds of smoke parted, and they saw the wonderful Silver Palace standing on a plateau beyond the chasm.

The palace seemed to cast a spell over them all, and they felt the fever of the gold-hunter beginning to burn in their throbbing veins.

It was more than an hour after their arrival that the balloon began to fill with gas and Frank uttered a cheer as he saw the silk bulging like a bladder that is inflated with wind.

"Ha, ha!" laughed Bushnell, wildly. "In a few minutes we'll go sailin'

over ther gulf, right through ther smoke, ter ther Silver Palace. Ha, ha, ha!"

The man's face was flushed till it was nearly purple, and his eyes were bloodshot. The fever had fastened itself firmly upon him.

More and more did the balloon expand. Bushnell had brought out a folding car, which he securely attached.

"In ten minutes more we'll be ready for the trip!" he shouted.

At that instant a series of wild cries reached their ears, and, turning swiftly, they saw a band of dark-faced men pouring through a fissure in the rocks to the north of them.

"Shimminy Gristmas!" cried Hans Dunnerwust, in terror. "Dot seddles us!"

"Who is it? Who are they?" fluttered the professor.

"They look like bandits," acknowledged Frank.

"It is Pacheco's band!" cried Bushnell, hastily securing his rifle.

"Ther pizen varmints hev come ten minutes too soon! Ther balloon would take us all over in another ten minutes, but now it won't carry more than two. We must hold ther skunks off till she fills."

"Right!" shouted Frank Merriwell. "And we must be ready to go the instant she does fill. We can't hold 'em back long, for we have no shelter here. Professor, Hans, into that car! Get in, I say, and be ready! We'll try to stand the whelps off till the balloon is inflated, but we must be ready to start at any instant."

Professor Scotch and Hans were hastily bundled into the car.

The bandits hesitated long enough to gather and prepare for the charge, with their chief in the lead. It was plain they saw the treasure-seekers had no shelter, and they meant to close in without delay.

"Reddy for 'em, Frank!" called Bushnell, dropping on one knee, his Winchester in his hands. "They're comin' right soon!"

This was true. With mad cries and a fusillade of shots, the bandits charged.

Bushnell opened fire, and Frank followed his example. Several of the bandits were seen to fall, but still the others came on.

"Lead won't stop 'em!" snarled the Westerner. "It'll be hand ter hand in a jiffy."

"And that means----"

"We'll get wiped out."

"The balloon----"

"Won't carry more'n two--possibly three. In with ye, boy! You may escape! It don't make any diffrunce 'bout an old c.o.o.n like me."

"Not much will I get in and leave you!" cried Frank. "We are partners in this expedition, and partners we'll stay to the end!"

"But ther others--ther professor an' ther Dutch boy! They might escape if----"

"They shall escape!"

Out flashed a knife in Frank Merriwell's hand, and, with one sweeping slash, he severed the strong rope that held the tugging, tossing balloon to the earth. Away shot the balloon, a cry of amazement and horror breaking from the lips of the professor and Hans.

"Mein gootness!" gasped the Dutch boy. "Vot vos happened?"

"I'll tell you," groaned the professor. "The balloon could not carry all four of us, and Frank Merriwell, like the n.o.ble, generous, hot-headed, foolish boy he is, refused to leave Bushnell. At the same time he would not doom us, and he cut the rope, setting the balloon free. He has remained behind to die at Bushnell's side."

"Led me git oudt!" sobbed Hans. "I vant to go pack und die mit him!"

"It was too late now. Look--see there! We are directly over the Silver Palace! What a beautiful----"

The professor's words were interrupted by a frightful rumbling roar that came up from the gulf surrounding the plateau on which the palace stood.

All the way around that gulf a sheet of flame seemed to leap upward through smoke, and then, paralyzed, helpless, hypnotized by the spectacle, they saw the plateau and the palace sink and disappear into the blackness of a great void. Then, like a black funeral pall, the smoke rolled up about them and shut off their view.

But they knew that never again would the eyes of any human being behold the marvelous Silver Palace of the Sierra Madre Mountains.

When the balloon had ascended higher another current of air was encountered, and the course changed. Away they floated over the mountain peaks and out beyond the great range.

At last they came down, made a safe landing, and, to their satisfaction, found themselves within a mile of Huejugilla el Alto.

They had escaped the most frightful perils, but Professor Scotch's heart lay like lead in his bosom, and Hans Dunnerwust was not to be comforted, for they had left Frank Merriwell to his doom.

In Huejugilla el Alto they remained four days, neither of them seeming to have energy enough to do anything.

And, on the fourth day, Frank, Al Bushnell, and two others rode into town and stopped at the hotel.

Picture the meeting between Frank and his friends! Hans shed nearly a bucketful of joyful tears, and Professor Scotch actually swooned from sheer amazement and delight. When the professor recovered, he clung to Frank's hands, saying: