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.