"Well, not exactly after," answered Tom, "but within an hour or so. Why do you ask?"
But Mr. Damon did not answer. Something on the floor of the shed, amid a pile of blackened and charred pieces of wood, attracted his attention. He stooped over and picked it up.
"Is this yours?" he asked Tom.
"No. What is it?"
The object looked like a small iron ball, with a tube about half an inch in diameter projecting slightly from it. Tom took it.
"Why, it looks like an infernal machine or a dynamite bomb," he said. "I wonder where it came from? Guess I'd better drop it in a pail of water. Maybe Eradicate found it and brought it here. I never saw it before. Mr. Jackson, please hand me that pail of water. We'll soak this bomb."
"There is no need," said Mr. Damon, quietly. "It is harmless now. It has done its work. It was that which set fire to your shed, and which caused the stifling fumes."
"That?" cried Tom.
"Yes. This ball is hollow, and was filled with a chemical. It was dropped on the roof, and, after a certain time, the plug in the tube was eaten through, the chemicals ran out, set the roof ablaze, and, dripping down inside spread the choking odors that nearly prevented you from getting out your aeroplane."
"Are you sure of this?" asked the young inventor.