“You are very trusting,” sneered the professor.
By this time, Mr. Johnson had reached the hillside. Puffing from having hurried so fast, he gazed in bewilderment at the little group.
“What does this mean?” he inquired. “What caused the mine to explode?”
“It was set off by being dropped in the lake,” explained the major.
“You mean the explosion was not touched off by Professor Bettenridge’s invention?”
“The machine had nothing whatsoever to do with it,” Penny explained. “Professor Bettenridge and his accomplice, Webb Nelson, have been doctoring the mines with a powder and an outer shield which dissolves in water. They hoped to sell the worthless machine to you before you discovered the truth.”
The information stunned Mr. Johnson, but recovering, he turned furiously upon Professor Bettenridge.
“You cheap trickster!” he shouted. “I’ll have you arrested for this!”
“Have you given the man any money?” Mr. Parker inquired.
“A thousand dollars for an option on the machine. The rest was to have been paid tonight.”