Sitting down on the sand, she nervously watched until the boat faded into the black of the night. Presently, she heard a splash which told her that the mine had been lowered overboard. Anxiously, she waited for the boat to return.
“Why don’t they come?” she thought, straining to hear the sound of oars. “If the explosion should go off while they’re still out there—”
Then she heard the boat coming and breathed in relief. Soon the craft grated on sand, and the three men leaped out.
“Perhaps my theory is wrong,” the major commented, as they all huddled together, waiting. “The mine should have gone off by this time.”
Several minutes elapsed and still nothing happened. And then, as the group became convinced their plan had failed, there came a terrific explosion which sent flame and water high above the lake’s surface.
CHAPTER
21
IN SEARCH OF WEBB
“Beautiful! Beautiful!” chuckled the major as the flames began to die away. “That proves our theory. No machine is required to set off the mines—only the action of water.”
“Professor Bettenridge must have heard the explosion!” Penny exclaimed, fairly beside herself with excitement. “What will happen now?”
“If human nature runs true to form, he will soon come here to investigate,” the major predicted.
The four stepped back into the dense growth of trees to wait. Within five minutes they observed two shadowy figures scurrying down the path toward the shack where the mines were stored. As they came closer, Penny recognized the professor and his wife.