"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 stiffling 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.
"Positive. I read about these bombs recently. A German invented them to be used in attacking a besieged city in case of war."
"But how did this one get on my shed roof?" asked Tom.
"It was dropped there by the mysterious airship!" exclaimed the odd man. "That was why
