Carter pulled a rubber cloth, designed to keep the instruments from moisture, off the table that held them. The boys regarded the set approvingly. It was a powerful one of the latest type. Evidently Fennell had not stinted himself on the price of his hobby.
Power was furnished from a dynamo run by a small gasoline engine. Fennell, so Carter said, had complained of trouble with this engine. Before starting it, therefore, Jack looked it over. He soon located the trouble—in the timer—and adjusted it. Then he started the engine. Soon the dynamo began to buzz loudly.
“Now then, I guess we’re all ready,” said Jack.
He sat himself down at the sending lever, first setting the switch, and then began sending out the submarine’s secret call.
“W-S! W-S! W-S!”
The spark crackled and blazed as it leaped across its terminals, but that was the only sound in the place except the distant roar of the surf. Again and again, for half an hour or more, Jack continued to call, stopping every now and then to adjust his receiver and listen for a reply.
Once he caught an answer, but it was only a steamer on her way to the West Indies.
Suddenly Jack gave a cry of triumph.
“What a double-dyed idiot I am!” he exclaimed. “I haven’t even had the sense to adjust this instrument to the same wave lengths as those of the White Shark’s set!”
Bending forward, he quickly made the necessary adjustments in the condenser. Then once more he sent the call vibrating into the caverns of space.