Critically he looked at the powerful explosive. As he did so a change came over his face.
"Here, Koku!" the young inventor said. "Where did you get this?"
"In cave, Master."
"Is there any more left?"
"Only enough for this one shoot."
"By Jove!" muttered Tom. "There's been some trick played here!" and he set off on a run toward the bomb-proof.
"What's the matter?" cried Ned, as he noticed the agitation of his chum.
"The powder has been doped!" yelled Tom. "Something has been put in it to make it nonexplosive. It's no good. It wouldn't send that shell a thousand yards, and it's got to go five miles to do any good. My plan won't work."
"Doped the powder?" gasped Ned. "Who could have done it?"
"I don't know. There must have been some spy at work. Quick, run and ask the foreman if any of his men are missing. I'll see if there's enough of the good powder left to break down the barrier!"