But the boys did not wait for this.  As soon as the case was over they hastened back to the Wondership.  The run home was made without incident and it was not till the Wondership was safely in its shed that Jack suddenly thought of the odd cylinder of lead that he had picked up by the man’s side as he lay on the road.

“I ought to have left it at the hospital,” he thought, “but I entirely forgot it.”

He drew it out and looked at it.  He now saw that the lead cylinder enclosed a glass vial carefully corked and sealed.  The bottle was wrapped in flannel.  Jack could not withstand the temptation of pulling it out and looking at it.  He hardly knew what he had expected to see, but he was distinctly disappointed, as was Tom, to find that the carefully protected vial contained nothing more than some dark, almost black, stuff that looked like sand.  In it were particles that glittered like mica.

“Pshaw!” he exclaimed in a disappointed tone, “nothing but a bottle full of sand.  Wonder why in the world that fellow carried trash like that so carefully wrapped up for?”

The solution of the question, which was near at hand, was to have an important bearing on the lives of the Boy Inventors, and that in the immediate future.

CHAPTER XIII.

The leaden tube.

The following day, while they were experimenting and practicing with the radio telephone, the boys received word that the man in the hospital was conscious and wished to see them, if possible.

“Perhaps now we shall get some explanation of that queer tubeful of sand,” said Jack, as he hung up the telephone receiver, having informed the physician that they would be at the hospital shortly.

“It’s certainly a queer sort of thing for a man to carry about—­a glass vial full of black grit so carefully protected, unless he is crazy or something,” commented Tom.

“I think that there is some explanation back of all this,” said Jack, “and for my part the sooner we get to the hospital, the better I shall be pleased.  The man told the doctor he was a miner and his name is Zeb Cummings.  Perhaps that sand is gold-bearing or something like that.”

“That might be the case,” agreed Tom.

The boys decided to take out the electric car.  It was in perfect running order and the indicator showed that there was plenty of electricity in storage for the start.  They told Mr. Chadwick where they were going and then rolled out of the High Towers gates onto the broad, smooth road bordered with pleasant green elms.

They bowled along smoothly and silently with the car working as perfectly as delicate clockwork.  They had gone about a mile from the house and were on a steep grade which the car took as easily as if it had been going down hill, when their attention was attracted by a sudden shout from the vicinity.