AND ALSO GETS A SURPRISE.

“Let me out of here,” cried Joe, rattling the door.

He felt that his liberty came first and that the time for questioning Hank would come later.

“Sure, I’ll let you out,” responded Hank, “but how under the sun did you get in there?”

“I was shoved in here and then the door was locked.”

“Who by?”

“Let me out first. I’ll tell you that later.”

“All right. The key is in the padlock. I’ll have you out in a jiffy.”

Hank’s behavior puzzled Joe. He did not appear to be belligerent or threatening. On the contrary, he seemed to be only too anxious to do a good turn to another youth in distress.

“Well, this beats rooster fighting!” exclaimed Hank, as Joe stepped out into the room. “You surely couldn’t have locked yourself in there. How did you happen to get in such a fix?”

“I’ll tell you all about that later,” said Joe hurriedly; “but I want to thank you, Hank Harley, for what you’ve done for me. It’s a big favor and I’m grateful for it.”

“That’s all right,” murmured Hank rather shamefacedly, “I reckon it was up to me to do something for you fellows after the other day’s work.”

Joe looked at him in surprise. What did this new attitude mean? True, Hank had taken no active part in the kidnapping of Nat, but he had made no move to prevent it; and yet here he was, apparently seeking their friendship. But the boy had no time to devote to speculation or questioning right then.

His sharp eyes had spied two pieces of paper lying on the floor near the wireless instruments. He eagerly picked them up and then gave an exclamation of delight.

“Why, those fellows have dropped the cipher and the key to it,” he exclaimed as he scanned the two sheets, “and here’s the message written out, too. Well, if this isn’t real luck!”

Knitting his forehead in thought, Joe went painstakingly over the message. It contained words he recollected having heard the intruding operator use. Then he took a pencil and with the help of the key managed to turn the meaningless message into plain English. This is what he wrote down:

“Leave Vesta before arrival at Vancouver. San Diego police have wired to arrest you there.”

“Phew!” whistled Joe, “so that was the game, eh? No wonder those fellows didn’t want to send their despatch from a land office! They were warning a friend, apparently a confederate of theirs in crime. Well, the rascals! I’ll fix it so that their warning will fall flat.”

He began sending out calls broadcast for the Vesta. It was some time before he raised her a hundred miles or more to the north of Goat Island. When he finally got in connection with the steamer, he requested the operator to transmit a private and confidential message to the captain. Then he sent word that the man to whom the two confederates had wirelessed was in all probability a criminal, and that it would be wise to keep him under surveillance and hand him over to the police at the first opportunity. When he had done this and received warm thanks for it, Joe began to try to raise the authorities ashore. He succeeded in getting a message into Santa Barbara police headquarters, which replied that they would be on the lookout for the two men who had visited the island. The information concerning the passenger on the Vesta was transmitted by the local authorities up the coast as far as Vancouver.

“Well, that’s a good job done,” sighed the lad contentedly, as he shoved his chair back and grounded his instruments. “Now then, if only they can nail those two fellows ashore, the wireless on Goat Island will have justified its existence for this day at any rate.”

All this time Hank Harley, a tall, raw-boned youth with big awkward hands and feet, had been looking on at Joe’s activities with much the same expression as a small boy gazing at a magician. It was plain that to Hank the whole thing savored of mystery. He stared at Joe with such wonderment and admiration that the boy could not help smiling.

“Were you talking to some one with that thing?” he asked incredulously.

“I certainly was. I was giving some information to a ship more than a hundred miles off.”

“Sho! Go on, now. Was you, honest?”

“Just as true as I’m sitting here,” replied Joe, but he saw that Hank’s face bore an expression of disbelief, and doubted if he would be able to explain to the unsophisticated youth the rather intricate theory of the wireless. He contented himself, therefore, by replying:

“I felt just the same way as you do about it, Hank, till I found out for myself just what wonderful things the wireless could accomplish.”

Hank, with a look of keen curiosity on his rough features stepped close to the instruments. He cautiously stretched out his gnarled fingers and touched the detector. The next instant he gave a howl of pain and bounded up till his head almost touched the roof of the shanty.

“Wow! Ow! Ouch!” he yelled at the top of his voice.

“What on earth is the matter?” demanded Joe, who had not seen Hank’s movement.

“Ouch! She bit!”

“She? Who?”

“Them things thar,” and Hank pointed to the instruments.

Joe couldn’t help laughing at Hank’s woebegone and alarmed expression as the young fisherman rubbed his arm.

“That wasn’t a bite, Hank, that was an electric shock. I wouldn’t advise you to tamper with the instruments again. Come here and I’ll show you how to work the key.”

“What, me? No, siree bob,” and Hank shook his head with deep conviction. “Let sleeping dawgs lie, says I. I wouldn’t touch that thar thing ag’in fer a new fishing boat. Wow, but the sparks flew!”

“It was lucky for you that we are not operating a high power station,” declared Joe. “Had we been doing so you might have been knocked out.”

“Sho! Killed dead?”

“Maybe. At the big stations the electric forces in the atmosphere are so strong that visitors cannot bring their watches into the operating room, unless they want to run the risk of seriously disarranging the mechanism.”

Hank looked prepared to believe anything by this time.

“Say, Joe,” he said, “now that we’ve buried the hatchet, s’pose you tell me something about how this contraption works.”

“It’s rather hard to explain in simple language, Hank, and I guess there are heaps of fellows just like you who’d like to understand the first principles of wireless without tackling a lot of dry text books, so here goes.”

“Let her go,” said Hank, knitting his brows and preparing to assimilate knowledge with a determined look on his rugged features.

“Of course you know about the waves of the sea,” began Joe. “Well, the air, or more properly the ether, is full of just such waves. But they are not set in motion till a disturbing element answering to a storm or a wind at sea is set loose among them. For instance, when I depress this key, I set loose an electric shock that agitates the ether and sends out waves. These waves may be long or short as I desire, according to the power of the shock sent out.

“In 1888 a Professor Hertz began the first attempts to utilize these waves to send messages through the air. In a crude way he succeeded, and paved the way for his followers along these lines. Hertz found that heat and light are all electric waves. The waves that he set in motion from his apparatus bear his name, Hertzian waves.”

“Then all the air is full of waves?” asked Hank, looking about him in a rather scared sort of way, as if he rather expected to be engulfed in some atmospheric disturbance at any time and was preparing to swim for his life.

“That’s it, Hank, you’re catching on fine. But understand, the waves require some force to agitate them. It’s like a mill pond, the air is, quite smooth till you chuck a stone into it, and then waves begin spreading out in all directions.”

Hank nodded as if he quite understood this homely illustration.

“Heave ahead,” he said, settling back in his seat.

“All right,” smiled Joe. “Now you see my detector here,—quite an elaborate bit of mechanism, isn’t it?”

“Yep, that’s what bit me,” muttered Hank, rubbing his arm once more at the recollection.

“Well, Hertz had to make his detector just out of a circle of wire with a gap in it. A screw adjustment lengthened or shortened the distance between the ends of the wire, making the gap larger or smaller. The waves, as they came in, were registered on this detector in the form of minute sparks. Is this all clear to you?”

“Oh, as clear as mud,” was the non-committal reply, with a wave of the hand.

“In 1895, Sir Oliver Lodge detected waves from an oscillator over a distance of forty yards, using a filings tube coherer, a galvanometer and a cell.”

“Hey, hey, hard aport there!” cried Hank. “You’re out of soundings, mate.”

“Well, that is a little technical, I’ll admit,” smiled Joe. “I’ll try and get down to plainer language.”

“Yep, my head ain’t tough enough to take in all that. It’s swimming now as if you’d chucked a dictionary at it,” growled Hank. “Tell me the names of them biting jiggers on the table thar, and what they’re supposed to do.”

“Very well. This,” touching it, “is the coil or transformer. That produces the spark that slips up into the aerials, those wires over our heads, and sends it shooting off into space just like that stone you might chuck in the pond.”

“Um-hum, that’s all clear enough. Heave ahead.”

“Now you see this little appliance? That is the vibrator. By that I can regulate the length and ‘fatness’ of my spark. Now when I press down the key like this——”

S-s-scrack!

Hank almost jumped from his seat as the green spark whined and leaped between the terminals.

“——well, that is a dot. If I make the contact longer, it forms a dash. Of course you know the Morse alphabet is made up of dots and dashes. For instance the letter A is .—.”

To illustrate Joe made the dot-dash sign, at which Hank blinked his eyes, but resolutely suppressed other symptoms of nervousness.

“And so on through the alphabet. Each letter has its own combination of dots and dashes. The only instruments needed in a simple set are the coil, spark-gap, wireless key and batteries; that is, for a sending set. Now we come to the receiving part of it.

“Suppose another operator miles away has been sending out into space the dot-dash just as I have been doing. If I had my receivers on, that is, those telephone-like things that I put on my head and over my ears, why then I’d have heard it, providing my apparatus was tuned to his wave lengths.”

“Hold hard! Hold hard! I don’t quite get that.”

“Simple enough. As I told you, various shocks of current produce various wave lengths. Well, suppose my receiving apparatus is only adjusted to receive a wave length of one thousand feet, and he is sending a wave of one thousand two hundred feet, then my apparatus will not be ‘in tune’ with his. That is, I shouldn’t be able to hear him.”

“Wa’al, how d’ye fix that—by touching off them biting things?” asked Hank. “Look a’out!” he added, as he saw Joe’s hand move toward the receiving tuning coil, “you ought’er have them things muzzled. If they bit you in the dog-days you’d git hydrophoby, sure as cock-fightin’.”

“Now then, Hank, a receiving tuning coil is used to adjust the wave lengths of the receiving circuits. This tuning, as it is called, is very simple. See, I move these sliding contacts along a bar, at the same time listening in. As soon as I am ‘in tune,’ I hear the dots and dashes from the other chap begin beating into my ears. Easy, isn’t it?”

“Humph, ’bout as easy as walkin’ a tight rope or running an air-ship! Joe, I couldn’t larn nothun’ ’bout such didoes in a billion, trillion of years.”

“In order to get the waves from the aerials into the receivers at my ears, they have to filter through the detector——”

“That’s the thing that bit me, that d’tector.”

“——through the detector, which consists of two mineral points in very delicate contact.”

“But is the blamed thing of any real use?” Hank wanted to be informed.