Chapter Sixteen. A Mysterious Fire

For a few moments Tom did not know what to think. Not that the sight of aeroplanes in flight were any novelty to him, but to see one flying over his house in the dead of night was a little out of the ordinary. Then, as he realized that night-flights were becoming more common, Tom tried to make out the details of the craft.

"I wish I had brought the night glasses with me," he said aloud.

"Here they are," spoke a voice at his side, and so suddenly that Tom was startled. He looked down, and saw Mr. Jackson standing beside him.

"Did you hear the noise, too?" the lad asked the engineer.

"Yes. It woke me up. Then I heard you moving around, and I heard you come up here. I thought maybe it was a flight of meteors you'd come to see, and I knew the glasses would be handy, so I stopped for them. Take a look, Tom. It's an aeroplane; isn't it?"

"Yes, and not moving very fast, either. They seem to be circling around here."

The young inventor was peering through the binoculars, and, as soon as he had the mysterious craft in focus, he cried:

"Look, Mr. Jackson, it's a new kind of monoplane. I never saw one like it before. I wonder who could have invented that? It's something like a santos-Dumont and a Bleriot, with some features of Cornu's Helicopter. That's a queer machine."

"It certainly is," agreed the engineer, who was now sighting through the glasses. In spite of the darkness the binoculars brought out the peculiarities of the aeroplane with considerable distinctness.

"Can you make out who are in it?" asked Tom.

"No," answered Mr. Jackson. "You try."

But Tom had no better luck. There were two persons in the odd machine, which was slowly flying along, moving in a great circle, with the Swift house for its center.

"I wonder why they're hanging around here?" asked Tom, suspiciously.

"Perhaps they want to talk to you," suggested Mr. Jackson. "They may be fellow inventor--perhaps one of them is that Philadelphia man who had the Whizzer."

"No," replied the lad. "He would have sent me word if he intended calling on me. Those are strangers, I think. There they are, coming back again."

The mysterious aeroplane was once more circling toward the watchers on the roof. There was a movement on the steps, near which Tom was standing, and his father came up.

"Is anything the matter?" he asked anxiously.

"Only a queer craft circling around up here," was the reply. "Come and see, dad."

Mr. Swift ascended to the roof. The aeroplane was higher now, and those in her could not so easily be made out. Tom felt a vague sense of fear, as though he was being watched by the evil eyes of his enemies. More than