“Whatever you do, don’t get into an argument with the professor about your camera until after the test,” Penny pleaded as they started up the slope again. “I want to watch the demonstration. If you accuse him of deliberately keeping the camera, he may throw us out.”
“Okay, I’ll wait,” Salt promised.
Reaching the cabin, the pair became instantly aware of a tenseness in the attitude of the professor and his wife. Although they did not tell the newcomers they were unwelcome, it was evident by their expressions that they distrusted Penny and Salt.
Professor Bettenridge stood behind his machine, explaining its many parts to the awed spectators. Penny could make nothing of the technical jargon.
“The demonstration will soon start,” the professor declared, looking at his watch. “I will turn on the motors now, as they must heat for several minutes.”
He turned several switches and the room was filled with a low humming sound. Two tiny lights buried deep in the complicated mechanism began to glow a cherry red. The professor bent low over the machine, frowning thoughtfully. He adjusted three of the concave mirrors, and switched on another motor.
Despite a dubious attitude, Penny found herself becoming deeply impressed. Was it possible, she wondered, that she had misjudged the professor and his machine? She dismissed the thought. The mine never would explode unless it had been tampered with—she was certain of that.
“Watch closely now,” the professor directed. “At any moment my assistant will signal with his lantern that he has dropped the mine and is safely away from the area.”
The professor’s wife had gone to the doorway. Tensely she watched the lake. Minutes passed. Then from out on the water, there came a moving circle of red—the signal from Webb.
“Now!” exclaimed the professor’s wife.