Radio Boys in the Secret Service; Or, Cast Away on an Iceberg by J. W. Duffield

“Good-by and good luck, Guy,” said Walter Burton as his twin brother, with small traveling bag in one hand and amber glasses protecting his supersensitive eyes, was about to step aboard a south-bound train at the Ferncliffe station one clear, crisp winter-end day. “Send me a wireless message from Europe, and I’ll be listening in and catch it.”
“I’d like to, Walt,” was Guy’s smiling answer; “but I’m afraid that would be extravagant. I’ll tell you what I’ll do, though. When we get to New York, I’ll hunt up Vacuum Tube and send you a message from his station. You know he invited us to come and see him any time we were in New York.”
“All right,” agreed Walter. “When’ll you send it?”
“At 4 o’clock tomorrow if he’s home.”