Part 24 (1/2)

”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 att.i.tude, 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 a.s.sistant 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 pa.s.sed. Then from out on the water, there came a moving circle of red--the signal from Webb.

”Now!” exclaimed the professor's wife.

Everyone in the little cabin held his breath. Dramatically, Professor Bettenridge took a metal tuning fork and struck it sharply against the crystal ball in the center of his machine.

”It will take a moment for the sound to reach the lake,” he said softly.

”But only a moment. Watch closely.”

All persons in the room crowded to the door and the windows. Suddenly a huge burst of flame appeared on the lake, fanning out on the surface of the water. A moment later came the dull boom of a terrific explosion.

CHAPTER 16 _SUSPICION_

Everyone who witnessed the spectacular demonstration was awed by the sight of the flames rising above the lake. As they died away, Professor Bettenridge, strutting a bit, walked back to his machine and covered it with the canvas hood.

”Now are you satisfied?” he inquired triumphantly. ”Is there anyone here who doubts the remarkable possibilities of my invention?”

”It was a fine demonstration! Magnificent!” approved Mr. Johnson, fairly beside himself with excitement. ”I am convinced of the machine's worth and if we can agree upon terms I will write you a check tonight.”

Professor Bettenridge's expression did not change, but the brief glance he flashed his wife was not lost upon Penny or Salt.

”You understand, of course,” he said smoothly, ”that the Navy probably will insist upon ultimate purchase of the machine even if I relinquish owners.h.i.+p?”

”Certainly,” agreed Mr. Johnson. ”I should expect to make such a sale.

The machine would have no practical use except in warfare.”

Penny was tempted to ask the man if he considered it patriotic to try to obtain control of a machine in the hope of selling it to the government at a high profit to himself. But she wisely remained silent.

Salt, however, had a few pointed remarks to offer.

”How come,” he observed, ”that if this invention is so remarkable, the Navy hasn't already snapped it up?”

Professor Bettenridge froze him with a glance. ”Young man,” he said cuttingly, ”you evidently do not understand how government business is conducted. Negotiations take months to complete. My wife and I need cash, so for that reason, we are willing to sell the machine quickly.”

”Yesterday I understood you to say that Navy men were ready to complete the deal,” Penny interposed innocently. ”Did they change their minds?”

”Certainly not!” Professor Bettenridge's dark eyes flashed, and only by great effort did he maintain control of his temper. ”You understand that while their recommendation would eventually be acted upon, a sale still would take many months to complete.”

”Will your machine explode mines on land as well as in the water?” Salt inquired.