Tom kept on with his powder experiments. Mr. Damon helped him, for that gentleman had succeeded in putting the affairs of the wholesale drug business on a firm foundation, and there was no more trouble about getting the supplies of cinchona bark to market. The natives seemed to have taken kindly to the eccentric man, or perhaps it was the reputation of Tom Swift and his electric rifle that induced them to work hard.
It must not be supposed that Professor Bumper was idle all this while.
He came and went at odd times, accompanied by his little retinue of Indians, a guide and a native cook. He would come back to the tunnel camp, where he made his headquarters, travel stained, worn and weary, with disappointment showing on his face.
"No luck," he would report. "The hidden city of Pelone is still lost."
Then he would retire to his tent, to pour over his note-books, and make a new translation of the inscription on the golden plates. In a day or so, refreshed and rested, he would prepare for another start.
"I'll find it this time, surely!" he would exclaim, as he marched off up the mountain trail. "I have heard of a new valley, never before visited by a white man, in which there are some old ruins. I'm sure they must be those of Pelone."
But in a week or so he would come back, worn out and discouraged again.
"The ruins were only those of a native village," he would say. "No trace of an ancient civilization there."
The professor took little or no interest in the tunnel, though he expressed the hope that Tom and his friends would be successful. But industrial pursuits had no charm for the scientist. He only lived to find the hidden city which was to make him famous.
He heard the story of the queer shaft leading down into the bore under the mountain, and, for a time, hoped that might be some clue to the lost Pelone. But, after an examination, he decided it was but the shaft to some ancient mine which had not panned out, and so had been abandoned after having been fitted with a balanced rocky door, perhaps for some heathen religious rite.