Webb had lighted a lantern which he hung on a wall nail. Unaware that he was being watched, he squatted in front of the mine which bore Mr. Johnson’s initials, studying it thoughtfully.
Muttering to himself, he next took a powerful ratchet drill, and for a long time worked with it on the mine, boring a tiny but deep hole.
“I’m getting stiff in this position,” Penny whispered. “What is he doing, Salt?”
“Don’t know,” the photographer admitted, puzzled. “Apparently, he’s doctoring Mr. Johnson’s mine so it will explode tonight, but I’m not smart enough to figure how the trick will be accomplished.”
By now it was so dark that the pair in the tree no longer feared they would be seen. Keeping perfectly still, they watched the work in the room below.
“It’s clear why Professor Bettenridge set nine o’clock for the demonstration,” Salt whispered. “Webb needed all this time to get the mine ready.”
“And that’s why they brought it here instead of dumping it into the lake,” Penny added. “But how can they make the mine explode at exactly the right moment?”
After Webb had worked for a while longer, he arose and stretched his cramped muscles. Going to a cupboard, he removed a white powder from a glass tube, and carefully inserted it in the hole he had just made in the mine. As a final act, he sealed the tiny hole with another material, and polished the surface so that the place did not show.
“Slick work!” Salt commented. “By the time he’s through, no one ever could tell the mine has been touched! Certainly not that thick-skulled Johnson.”
Apparently satisfied with his work, Webb put away his tools, made a final inspection of the mine, and then left the shack. After carefully locking the door, he disappeared into the night.