“But they may be cargo ships in a convoy or airplanes going to Europe,” said Nancy. “Then why don’t we ask our Communications people in Washington whether they are using that wave-length.”
“Two good reasons,” Danny grinned. “We don’t know the wave-length we’re using and if we did the folks in Washington wouldn’t tell us.”
“Probably send an F. B. I. agent to look us up,” Sally said. “No, dearie! We’ve got to work it out all by ourselves.”
“Just give us time and we’ll make it,” Danny declared. Ah, yes, there was the rub. All too soon the bugle would blow and they would be scattered far and wide to new fields of endeavor.
They made some progress. One evening Danny exclaimed: “See here! The numbers they are sending—if they are numbers—are all odd. Seven, seventeen, thirty-one, forty-three. There’s not an even number in the lot.”
“That narrows it down,” said Sally.
“It sure does.”
Two evenings later Sally made a more important discovery.
“Look!” She jumped to her feet in her excitement, to point at a row of numbers. “Not one of them is evenly divisible. Seven, seventeen, thirty-seven, fifty-three, every last one of them. Does that mean anything?”
“It may mean a lot,” was Danny’s excited comment.