"It will be dark then," said Mr. Borious, "and if you can hover in your airship near at hand, and if Mr. Petrofsky can call out to his brother to run to him, we can take him up with us and get away before the guards know what we are doing."
"But aren't the prisoners chained?" asked Tom.
"No, they depend on guards to prevent escapes."
"Then we'll try that way," decided the young inventor.
On and on they sailed, the Falcon working admirably. Verst after verst was covered, and finally, one morning, Mr. Borious, who knew the country well, from having once been a prisoner there, said:
"We are now near the place. If we go any closer we may be observed. We had better remain hidden in some grove of trees so that at nightfall we can go forth to the rescue."
"But how can we find it after dark?" asked Ned.
"You can easily tell by the lights in the barracks," was the answer. "I can stand in the pilot house to direct you, for nearly all these exile prisons are alike. The prisoners will march in a long line from the mine. Then for the rescue."
It was tedious waiting that day, but it had to be done, and to Tom, who was anxious to effect
