lot.”

He placed a small instrument on top of a metal box, then connected it by a tube to a loud-speaker. After that he tuned in on the 750 meter wave length and spoke a few words into his transmitter. Having done this, he settled back as if to await an answer.

Presently a loud jumble of sound, resembling nothing quite so much as a flock of crows fighting over a carcass, began coming forth from the loud-speaker.

Joe Marion’s brow wrinkled. At the end of three seconds he exploded:

“Tune her up, why don’t you!”

Curlie grinned, but did not move.

“No use letting it go on like that,” expostulated Joe, making a move to take a hand in the business. “He might be sending something important.”

“He is,” said Curlie, pushing his companion back to his seat. “He’s saying something mighty important. That’s why I don’t change it. I told you I had something new. Can’t you wait to see it tried out?”

Sinking back into his place, Joe listened to the strange clack-clack in silence.

A few seconds later the sounds ceased. Quickly removing a small instrument and disconnecting the tube from the loud-speaker, Curlie tuned in on 350 and, a moment later, they were listening to a concert which was being broadcasted somewhere on the Pacific Coast.

“Do you mean to tell me that that thing is a phonograph?” said Jennings.

“No,” said Curlie, “I don’t. That music comes to us over five hundred miles of space, perhaps a thousand; Seattle, Vancouver, San Francisco, I don’t know which.”

Again the miner was silent.

Removing a small disc from the instrument which had produced the strange jumble of sounds, Curlie slipped it upon a second instrument which resembled a small phonograph.

“Now listen to this,” he said to Joe, as he shut off the radiophone.

From the phonograph-like instrument there came first a grating sound, then in a somewhat metallic but very distinct tone:

“Valdez speaking. Your man is still active. Doing much damage in air. Last night interrupted an important U. S. army order. Seemed nearer. Appears to be moving toward us. Location somewhere south of Fort Yukon. Advise speed and caution. N. T. S.”

“Well, now, what do you think of that!” exclaimed Joe.

“I think,” said Curlie, “that we have put one over on our old friend up north there who persists in raising hob in the air.

“You see,” he went on more soberly, “it’s a very recent invention. You slip a little affair on your sending instrument, which tears your tones all into little bits and sends them out as so much mental mince pie. But this little instrument here straightens them out for the person at the other end and gives them to him just as they have been spoken. I feel sure that the man we are after does not possess one of the outfits. That means that we may speak with Valdez at any time without fear of detection. All that an outside party gets is a jumble of sounds.

“If we ever get separated on the trail we may speak to one another in the same way. You have that small, reserve sending and receiving set on your sled and I am going to give you a set of these new instruments.

“Once more,” he smiled, “I want to state that it is my belief that if you keep your little radiophone dry and tuned up, it will help you out of any dangerous position.”

Had they known under what strange circumstances this belief would be tried in the days to come and on this very trip, the two boys might not have laughed quite so merrily as Curlie again threw on the radiophone and they listened to jazz being broadcasted from Seattle.

Joe, tired out from the day’s struggle over the glacier, feeling the cozy warmth of the fire, stretched himself out on his sleeping-bag and fell at once into a drowsy slumber.

“Here,” said Curlie, noting the eager manner in which Jennings listened to the bits of music and gossip which drifted in from the air, “you listen with this.” He snapped a receiver over the miner’s head. “I’ve got to shut off that loud-speaker. Want to listen in and see what I can catch.”

For a time he listened on short wave lengths for his friend, the Whisperer. At last, having given that up, he tuned in on long wave lengths and at once began picking up something.

Having tuned his instrument accurately and adjusted his coil aerial, he succeeded in listening in in a very satisfactory matter.

“Big business,” he whispered to himself. “Shouldn’t wonder if that was a clue.”

It was indeed big business that was flashing through the air that night. It was the report of a government official, the announcement of the securing of sufficient evidence at Nome, Alaska, to convict a bold band of smugglers who had been carrying valuable jewels, taken from rich families in Russia, into America by way of Alaska. These smugglers had escaped detection for some time by traveling in native skin-boats across Behring Straits. In some way, Curlie could hardly make out how, the great explorer Munson had been of assistance to the government in bringing these men to justice. Because of this service the government was instructing all its officials, especially wireless operators, to lend every assistance possible to Munson in his dash to the Pole.

“Don’t see how a fellow three thousand miles away can help an explorer reach the Pole,” Curlie told himself, “but I suppose there must be a way—”

His thoughts were cut short by an interruption to the message. Someone with a powerful sending set had cut loose into the air with his sparker. The result was utter bedlam of the air. Not one word could be recognized.

“That’s the man,” Curlie breathed excitedly, “that’s the fellow I’m after! Now for his location.”

His fingers moved rapidly from instrument to pencil and paper, then back to instrument again. There was a look of tense excitement on his face, such a look as comes upon the hunter as he sights a moose not a hundred yards away. Curlie was a born hunter, a hunter of the air. He had got scent of a prey, a dangerous prey, and was at this moment hunting him down.

“There,” he breathed as the bedlam ceased, and he drew the receiver from his head. “I know where you are, at least. You’re moving. I wonder if we’ll meet and when. I know what I’m going to say to you when we meet. Wonder if you know what you’re going to say to me!”

Having packed his instruments away, he stretched himself out before the fire to think. Events were moving on apace. It looked as if his journey would be shorter than he had at first believed it would be. You never could tell, though. He thought for the hundredth time of the Whisperer; wondered who she really was and why her whisper had been missing to-night.

At last, reaching over to Joe, he shook him into wakefulness and told him to turn in. Having undressed, he slipped on a suit of pajamas, crept into his sleeping-bag and was soon fast asleep.

CHAPTER IV
JOE MISSING

Curlie Carson was worried. As he sat on his rolled-up sleeping-bag in the tent which had been set with the usual care for a night’s comfort, his fingers drummed incessantly on the box which held his three-stage amplifier, while he muttered ever now and again:

“Wish he’d come. I don’t like the looks of it. What’s keeping him? That’s what I’d like to know.”

Joe was three hours overdue. After