The Radio Boys Trailing A Voice, Allen Chapman, 1922, pages v - vi:


    WITHIN a comparatively short time after this volume is published the human voice will be thrown across the Atlantic Ocean under conditions that will lead immediately to the establishment of permanent telephone communication with Europe by means of radio.
    Under the circumstances therefore the various uses of radio which are so aptly outlined in it will give the reader an idea of the tremendous strides that have been made in the art of communicating without wires during the past few months.
    Of these one of the most important, which by the way is dealt with to a large extent in the present volume, is that of running down crooks. It must not be forgotten that criminals, and those criminally intent are not slow to utilize the latest developments of the genius of man, and radio is useful to them also. However, the forces of law and order inevitably prevail, and radio therefore is going to be increasingly useful in our general police work.
    Another important use, as outlined in this volume, is in the detection of forest fires, and in fact generally protecting forest areas in conjunction with aircraft. With these two means hundreds of thousands of acres can now be patrolled in a single day more efficiently than a few acres were previously covered.
    Radio is an ideal boy's hobby, but it is not limited to youth. Nevertheless it offers a wonderful scope for the unquenchable enthusiasm that always accompanies the application of youthful endeavor, and it is a fact that the majority of the wonderful inventions and improvements that have been made in radio have been produced by young men.
    Since this book was written there has been produced in this country the most powerful vacuum tube in the world. In size it is small, but in output it is capable of producing 100 kilowatts of electrical power. Three such tubes will cast the human voice across the Atlantic Ocean under any conditions, and transmit across the same vast space the world's grandest music. Ten of these tubes joined in parallel at any of the giant transmitting wireless telegraph stations would send telegraph code messages practically around the world.
Binns signature

Pages 9-17:



    "You fellows want to be sure to come round to my house to-night and listen in on the radio concert," said Bob Layton to a group of his chums, as they were walking along the main street of Clintonia one day in the early spring.
    "I'll be there with bells on," replied Joe Atwood, as he kicked a piece of ice from his path. "Trust me not to overlook anything when it comes to radio. I'm getting to be more and more of a fan with every day that passes. Mother insists that I talk of it in my sleep, but I guess she's only fooling."
    "Count on yours truly too," chimed in Herb Fennington. "I got stirred up about radio a little later than the rest of you fellows, but now I'm making up for lost time. Slow but sure is my motto."
    Just then Mr. Preston, the principal of the high school, came along.
    "How are you, boys?" said Mr. Preston, with a smile. "You seem to be having a good time."
    "Jimmy is," returned Herb, and Jimmy covertly shook his fist at him. "We're making the most of the snow and ice while it lasts."
    "Well, I don't think it will last much longer," surmised Mr. Preston, as he walked along with them. "As a matter of fact, winter is 'lingering in the lap of spring' a good deal longer than usual this year."
    "I suppose you had a pleasant time in Washington?" remarked Joe inquiringly, referring to a trip from which the principal had returned only a few days before.
    "I did, indeed," was the reply. "To my mind it's the most interesting city in the country. I've been there a number of times, and yet I always leave there with regret. There's the Capitol, the noblest building on this continent and to my mind the finest in the world. Then there's the Congressional Library, only second to it in beauty, and the Washington Monument soaring into the air to a height of five hundred and fifty-five feet, and the superb Lincoln Memorial, and a host of other things scarcely less wonderful.
    "But the pleasantest recollection I have of the trip," he went on, "was the speech I heard the President make just before I came away. It was simply magnificent."
    "It sure was," replied Bob enthusiastically. "Every word of it was worth remembering. He certainly knows how to put things."
    "I suppose you read it in the newspaper the next day," said Mr. Preston, glancing at him.
    "Better than that," responded Bob, with a smile. "We all heard it over the radio while he was making it."
    "Indeed!" replied the principal. "Then you boys heard it even before I did."
    "What do you mean?" asked Joe, in some bewilderment. "I understood that you were in the crowd that listened to him."
    "So I was," Mr. Preston answered, in evident enjoyment of their mystification. "I sat right before him while he was speaking, not more than a hundred feet away, saw the motion of his lips as the words fell from them and noted the changing expression of his features. And yet I say again that you boys heard him before I did."
    "I don't quite see," said Herb, in great perplexity. "You were only a hundred feet away and we were hundreds of miles away."
    "And if you had been thousands of miles away, what I said would still be true," affirmed Mr. Preston. "No doubt there were farmers out on the Western plains who heard him before I did.
    "You see it's like this," the schoolmaster went on to explain. "Sound travels through the air to a distance of a little over a hundred feet in the tenth part of a second. But in that same tenth of a second that it took the President's voice to reach me in the open air radio could have carried it eighteen thousand six hundred miles."
    "Whew!" exclaimed Jimmy. "Eighteen thousand six hundred miles! Not feet, fellows, but miles!"
    "That's right," said Bob thoughtfully. "Though I never thought of it in just that way before. But it's a fact that radio travels at the rate of one hundred and eighty-six thousand miles a second."
    "Equal to about seven and a half times around the earth," observed the principal, smiling. "In other words, the people who were actually sitting in the presence of the President were the very last to hear what he said.
    "Put it in still another way. Suppose the President were speaking through a megaphone in addition to the radio and by the use of the megaphone the voice was carried to people in the audience a third of a mile away. By the time those persons heard it, the man in the moon could have heard it too--that is," he added, with a laugh, "supposing there really were a man in the moon and that he had a radio receiving set."
    "It surely sounds like fairyland," murmured Joe.
    "Radio is the fairyland of science," replied Mr. Preston, with enthusiasm, "in the sense that it is full of wonder and romance. But there the similarity ceases. Fairyland is a creation of the fancy or the imagination. Radio is based upon the solid rock of scientific truth. Its principles are as certain as those of mathematics. Its problems can be demonstrated as exactly as that two and two make four. But it's full of what seem to be miracles until they are shown to be facts. And there's scarcely a day that passes without a new one of these 'miracles' coming to light."
    He had reached his corner by this time, and with a pleasant wave of his hand he left them.
    "He sure is a thirty-third degree radio fan," mused Joe, as they watched his retreating figure.
    "Just as most all bright men are becoming," declared Bob. "The time is coming when a man who doesn't know about radio or isn't interested in it will be looked on as a man without intelligence."
    "The reason why I wanted you fellows to be sure to be on hand to-night," resumed Bob, as they walked along, "was that I saw in the program of the Newark station in the newspaper this morning that Larry Bartlett was down for an entirely new stunt. You know what a hit he made with his imitations of birds."
    "He sure did," agreed Joe. "To my mind he had it all over the birds themselves. I never got tired listening to him."
    "He certainly was a dabster at it," chimed in Jimmy.
    "Now he's going in to imitate animals," explained Bob. "I understand that he's been haunting the Zoo for weeks in every minute of his spare time studying the bears and lions and tigers and elephants and snakes, and getting their roars and growls and trumpeting and hisses down to a fine point. I bet he'll be a riot when he gives them to us over the radio."
    "He sure will," assented Herb. "He's got the natural gift in the first place, and then he practices and practices until he's got everything down to perfection."
    "He's a natural entertainer," affirmed Bob. "I tell you, fellows, we never did a better day's work than when we got Larry that job at the sending station. Not only was it a good thing for Larry himself when he was down and out, but think of the pleasure he's been able to give to hundreds of thousands of people. I'll bet there's no feature on the program that is waited for more eagerly than his."
Pages 36-42:

    A little while afterward the other three boys came over to Bob's house to listen in on the radio concert. So much time, however, had been taken up in discussing the afternoon's adventure that they missed Larry's offering, which was among the first on the program. This was a keen disappointment, which was tempered, however, by the probability that they could hear him some evening later in the week.
    "Sorry," remarked Joe. "But it only means that we still have a treat in store when the old boy begins to roar and growl and hiss so as to make us think that a whole menagerie has broken loose and is chasing us. In the meantime we can fix up that aerial so as to get a little better results."
    "Funny thing I noticed the other day," remarked Bob, as they embarked upon some experiments.
    "All sorts of funny things in the radio game," observed Joe. "Something new turns up every day. Things in your set that you think you can't do without you find you can do without and get results just about as usual."
    "Just what I was going to tell you," returned Bob. "You must be something of a prophet."
    "Oh, I wouldn't go quite so far as to say that," replied Joe, with mock modesty.
    "Isn't he the shrinking violet?" chaffed Jimmy. "Stop your kidding, you boobs, and let a regular fellow talk," chided Bob. "What I was going to say was that while I was tinkering with the set I disconnected the ground wire. Of course I thought that would put the receiver out of business for the time, and I was almost knocked silly when I found that I could hear the concert that was going on just about as well as though the wire had been connected. How do you account for that?"
    "Don't account for it at all," replied Herb. "Probably just a freak, and might not happen again in a thousand times. Likely it was one of the unexplainable things that happen once in a while. Maybe there was a ground connection of some kind, if not by the wire. I wouldn't bank on it."
    "It's queer, too, how many kinds of things can be used as aerials," put in Joe. "I heard the other day of a man in an apartment house where the owner objected to aerials, who used the clothesline for that purpose. The wire ran through the rope, which covered it so that it couldn't be seen. It didn't prevent its use as a clothesline either, for he could hear perfectly when the wash was hanging on it."
    "Oh, almost anything will do as an aerial," chimed in Jimmy. "The rib of an umbrella, the rainspout at the side of the house, the springs of a bed give good results. And that's one of the mighty good things about radio. People that have to count the pennies don't have to buy a lot of expensive materials. They can put a set together with almost any old thing that happens to be knocking around the house."
    Bob had been working steadily, and, as the room was warm, his hands were moist with perspiration. He had unhooked an insulated copper wire that led to his outside aerial. His head phones were on, as he had been listening to the radio concert while he worked.
    "I'll have to miss the rest of that selection, I guess," he remarked regretfully, as he unhooked the wire. "It's a pity, too, for that's one of the finest violin solos I ever heard. Great Scott! What does that mean?"
    The ejaculation was wrenched from him by the fact that although he had disconnected the wire he still heard the music--a little fainter than before but still with every note distinct.
    He could scarcely believe his ears and looked at his friends in great bewilderment.
    "What's the matter?" asked Joe, jumping to his feet. "Get a shock?"
    "Not in the sense you mean, but in another way, yes," replied Bob, still holding the exposed end of the copper wire in his fingers. "What do you think of that, fellows? I'm an aerial!"
    "Come out of your trance," adjured Herb unbelievingly. "They talk that way in the insane asylums."
    "Clap on your headphones," cried Bob, too intent on his discovery to pay any attention to the gibe.
    They did so, and were amazed at hearing the selection as plainly as did Bob himself.
    The latter had been holding the disconnected wire so that his fingers just touched the uncovered copper portion at the end. Now he hastily scraped off several inches of the insulation and grasped the copper wire with his hand. Instantly the volume of sound grew perceptibly greater.
    Hardly knowing what to make of it, he scraped off still more of the insulation.
    "Here, you fellows," he shouted. "Each of you take hold of this."
    Joe was the first to respond, and the sound became louder. Then Herb and Jimmy followed suit, and it was evident that they served as amplifiers, for with each additional hand the music swelled to greater volume.
    The boys looked at each other as if asking whether this was all real or if they had suddenly been transferred to some realm of fancy. They would not have been greatly surprised to wake up suddenly and find that they had been dreaming.
    But there was no delusion about it and they listened without saying another word until, in a glorious strain of melody, the selection came to an end. Nor did they break the silence until a band orchestra was announced and crashed into a brilliant overture.
    While it was still in full swing, Bob had an inspiration. He took off his headphones and clamped them on to the phonograph that stood on a table near by. Instantly the music became intensified and filled the room. When all their hands were on the wire, it became so loud that they had to close the doors of the phonograph.
    "Well," gasped Bob, when the last strain had died away and the demonstration was complete, "that's something new on me."
    "Never dreamed of anything like it," said Joe, sinking back in his chair. "Of course we know that the human body has electrical capacity and that operators sometimes have to use metal shields to protect the tube from the influence of the hand. And in our loop aerial at Ocean Point you noticed that the receptivity of the tube was modified when we touched it with our fingers."
    "Of course, in theory," observed Bob thoughtfully, "the human body possesses inductance as well as capacity, and so might serve as an antenna. But I never thought of demonstrating it in practice."
    "So Bob is an aerial," grinned Herb. "I always knew he was a 'live wire,' but I never figured him out as an antenna."
    "And don't forget that if Bob is an aerial we're amplifiers," put in Jimmy.
    "There's glory enough for all," laughed Joe. "We'll have to tell Doctor Dale and Frank Brandon about this. We've got so many tips from them that it's about time we made it the other way around."
Pages 55-60:


    The radio boys had missed Larry's performance on the night that he had opened with his new repertoire, but they were bound not to be cheated of the second, which took place only a few nights later.
    They crowded eagerly about the radio set when their friend's turn was announced, and listened with a breathless interest, that was intensified by their warm personal regard for the performer, to the rendition of the cries of various animals with which Larry regaled them.
    The imitations were so lifelike that the boys might well have imagined they were in a zoölogical garden. Lions, tigers, bears, elephants, snakes, moose, and other specimens of the animal and the reptile tribes were imitated with a fidelity that was amazing. In addition, the renditions were interspersed with droll and lively comments by Larry that added immensely to the humor of the performance. When at last it was over, the boys broke out into enthusiastic hand-clapping that would have warmed Larry's heart, had he been able to hear it.
    "The old boy is all there!" chortled Bob enthusiastically.
    "He's a wonder!" ejaculated Joe. "No question there of a square peg in a round hole. He's found exactly the work in life he's specially fitted for."
    "And think of the audience he has," put in Jimmy. "At this very minute there are probably hundreds of thousands of people who have been tickled to death at his performance. Just suppose those people all clapped their hands at once just as we have done and we could hear it. Why, it would be like a young earthquake."
    At this moment the doorbell rang, and Dr. Dale was announced. He spent a few minutes with Mr. and Mrs. Layton, and then came up to have a little chat with the boys. This was one thing he never overlooked. His interest in and sympathy with the young were unbounded, and accounted largely for the influence that he exerted in the community.
    The radio boys greeted the minister warmly and gladly made room for him around the table. His coming was never felt by them to be an interruption. They regarded him almost as one of themselves. Apart, too, from the thorough liking they had for him as a man, they were exceedingly grateful to him for the help he had been to them in radio matters. He was their mentor, guide and friend.
    "I knew I'd find you busy with the radio," he said, with a genial smile.
    "We can't be torn away from it," replied Bob. "We think it's just the greatest thing that ever happened. Just now we've been listening to Larry Bartlett give his imitations of animals. You remember Larry?"
    "I certainly do," replied Dr. Dale. "And I remember how you boys helped him get his present position. It was one of the best things you ever did. He's certainly a finished artist. I heard him on his opening night, and I've laughed thinking of it many times since. He's a most amusing entertainer."
    It was the first opportunity the boys had had to tell the doctor of the night when Bob found that he was a human aerial, and he listened to the many details of the experiment with absorbed interest.
    "It's something new to me," he said. "You boys have reason to be gratified at having had a novel experience. That's the beauty of radio. Something new is always cropping up. Many of the other sciences have been more or less fully explored, and while none of them will ever be exhausted, their limits have been to some extent indicated. But in radio we're standing just on the threshold of a science whose infinite possibilities have not even been guessed. One discovery crowds so closely on the heels of another that we have all we can do to keep track of them.
    "I've just got back from a little trip up in New York State," he went on, as he settled himself more comfortably in his chair, "and I stopped off at Schenectady to look over the big radio station there. By great good luck, Marconi happened to be there on the same day----"
    "Marconi!" breathed Bob. "The father of wireless!"
    "Yes," smiled Dr. Dale. "Or if you want to put it in another way, the Christopher Columbus who discovered the New World of radio. I counted it a special privilege to get a glimpse of him. But what attracted my special attention in the little while I could spend there was a small tube about eighteen inches long and two inches in diameter which many radio experts think will completely revolutionize long distance radio communication."
    "You mean the Langmuir tube," said Joe. "I was reading of it the other day, and it seems to be a dandy."
    "It's a wonderful thing," replied the doctor. "Likely enough it will take the place of the great transatlantic plants which require so much room and such enormous machinery. It's practically noiseless. Direct current is sent into the wire through a complicated wire system and generates a high frequency current of tremendous power. I saw it working when it was connected with an apparatus carrying about fifteen thousand volts of electricity in a direct current. A small blue flame shot through the tube with scarcely a particle of noise. The broken impulse from the electrical generators behind the tube was sent through the tube to be flung off from the antenna into space in the dots and dashes of the international code. That little tube was not much bigger than a stick of dynamite, but was infinitely more powerful. I was so fascinated by it and all that it meant that it was hard work to tear myself away from it. It marks a great step forward in the field of radio."
    "It must have been wonderfully interesting," remarked Bob. "And yet I suppose that in a year or two something new will be invented that will put even that out of date."
    "It's practically certain that there will be," assented the doctor. "The miracles of to-day become the commonplaces of to-morrow. That fifty-kilowatt tube that develops twelve horsepower within its narrow walls of glass, wonderful as it is, is bound to be superseded by something better, and the inventor himself would be the first one to admit it. Some of the finest scientific brains in the country are working on the problem, and he would be a bold prophet and probably a false prophet that would set any bounds to its possibilities.
    "Radio is yet in its infancy," the doctor concluded, as he rose to go. "But one thing is certain. In the lifetime of those who witnessed its birth it will become a giant--but a benevolent giant who, instead of destroying will re-create our civilization."
Pages 63-96:


    By this time the lads had reached Bob's house. It was Saturday afternoon, and as the boys crowded noisily into the ball Bob noticed that his father was in the library and that he seemed to have company.
    He was starting upstairs with the other lads when his father came out of the library and called to him.
    "Come on in for a few minutes, boys," he said. "I have a friend here who is a man after your own hearts," and his eyes twinkled. "He's interested in radio."
    The boys needed no second invitation, for they never missed an opportunity of meeting any one who could tell them something about the wonders of radio.
    Mr. Layton's guest was lounging in one of the great chairs in the library, and from the moment the boys laid eyes on him they knew they were going to hear something of more than usual interest.
    The stranger was big, over six feet, and his face and hands were like a Cuban's, they were so dark. Even his fair hair seemed to have been burnt a darker hue by the sun. There was a tang of the great out-of-doors about him, a hint of open spaces and adventure that fascinated the radio boys.
    "This is my son, Mr. Bentley," said Mr. Layton to the lounging stranger, still with a twinkle in his eye. "And the other boys are his inseparable companions. Also I think they are almost as crazy about radio as you are."
    The stranger laughed and turned to Bob.
    "I've been upstairs to see your set," he said, adding heartily: "It's fine. I've seldom seen better amateur equipment."
    If Bob had liked this stranger before, it was nothing to what he felt for him now. To the radio boys, if any one praised their radio sets, this person, no matter who it was, promptly became their friend for life.
    "I'm glad you think it's pretty good," Bob said modestly. "We fellows have surely worked hard enough over it."
    "This gentleman here," said Mr. Layton to the boys, "ought to know quite a bit about radio. He operates an airplane in the service of our Government Forestry."
    "In the United States Forest Service?" cried Bob, breathlessly, eyeing the stranger with increasing interest. "And is your airplane equipped with radio?"
    "Very much so," replied Mr. Bentley. "It seems almost a fairy tale--what radio has done for the Forest Service."
    "I've read a lot about the fighting of forest fires," broke in Joe eagerly. "But I didn't know radio had anything to do with it."
    "It hadn't until the last few years," the visitor answered, adding, with a laugh. "But now it's pretty near the whole service!"
    "Won't you tell us something about what you do?" asked Bob.
    Mr. Bentley waved a deprecating hand while Mr. Layton leaned back in his chair with the air of one who is enjoying himself.
    "It isn't so much what I do," protested this interesting newcomer, while the boys hung upon his every word. "It is what radio has done in the fighting of forest fires that is the marvelous, the almost unbelievable, thing. The man who first conceived the idea of bringing radio into the wilderness had to meet and overcome the same discouragements that fall to the lot of every pioneer.
    "The government declared that the cost of carrying and setting up the radio apparatus would be greater than the loss occasioned every season by the terribly destructive forest fires. But there was a fellow named Adams who thought he knew better."
    "Adams!" repeated Bob breathlessly. "Wasn't he the fellow who had charge of the Mud Creek ranger station at Montana?"
    The visitor nodded and gazed at Bob with interest. "How did you know?" he asked.
    "Oh, I read something about him a while ago," answered Bob vaguely. He was chiefly interested in having Mr. Bentley go on.
    "I should think," said Herb, "that it would be pretty hard work carrying delicate radio apparatus into the lumber country."
    "You bet your life it is," replied Mr. Bentley. "The only way the apparatus can be carried is by means of pack horses, and as each horse can't carry more than a hundred and fifty pounds you see it takes quite a few of the animals to lug even an ordinary amount of apparatus.
    "The hardest part of the whole thing," he went on, warming to his recital as the boys were so evidently interested, "was packing the cumbersome storage batteries. These batteries were often lost in transit, too. If a pack horse happened to slip from the trail, its pack became loosened and went tumbling down the mountain side----"
    "That's the life!" interrupted Jimmy gleefully, and the visitor smiled at him.
    "You might not think so if you happened to be the one detailed to travel back over the almost impassable trails for the missing apparatus," observed Mr. Bentley ruefully. "It wasn't all fun, that pioneer installation of radio. Not by any means."
    "But radio turned the trick just the same," said Bob slangily. "I've read that a message that used to take two days to pass between ranger stations can be sent now in a few seconds."
    "Right!" exclaimed Mr. Bentley, his eyes glinting. "In a little while the saving in the cost of forest fires will than pay for the installation of radio. We nose out a fire and send word by wireless to the nearest station, before the fire fairly knows it's started."
    "But just what is it that you do?" asked Joe, with flattering eagerness.
    "I do scout work," was the reply. "I help patrol the fire line in cases of bad fires. The men fighting the fire generally carry a portable receiving apparatus along with them, and by that means, I, in my airplane, can report the progress of a fire and direct the distribution of the men."
    "It must be exciting work," said Herb enviously. "That's just the kind of life I'd like--plenty of adventure, something doing every minute."
    "There's usually plenty doing," agreed Mr. Bentley, with a likable grin. "We can't complain that our life is slow."
    "I should think," said Bob slowly, "that it might be dangerous, installing sets right there in the heavy timber."
    "That's what lots of radio engineers thought also," agreed Mr. Bentley. "But no such trouble has developed so far, and I guess it isn't likely to now."
    "Didn't they have some trouble in getting power enough for their sets?" asked Joe, with interest.
    "Yes, that was a serious drawback in the beginning," came the answer. "They had to design a special equipment--a sort of gasoline charging plant. In this way they were able to secure enough power for the charging of the storage batteries."
    Bob drew a long breath.
    "Wouldn't I have liked to be the one to fit up that first wireless station!" he cried enthusiastically. "Just think how that Mr. Adams must have felt when he received his first message through the air."
    "It wasn't all fun," the interesting visitor reminded the boys. "The station was of the crudest sort, you know. The first operator had a box to sit on and another box served as the support for his apparatus."
    "So much the better," retorted Bob stoutly.
    "A radio fan doesn't know or care, half the time, what he's sitting on."
    "Which proves," said Mr. Bentley, laughing, "that you are a real one!" And at this all the lads grinned.
    "But say," interrupted Joe, going back to the problem of power, "weren't the engineers able to think up something to take the place of the gasoline charging stations?"
    "Oh, yes. But not without a good deal of experimenting. Now they are using two hundred and seventy number two Burgess dry batteries. These, connecting in series, secure the required three hundred and fifty-volt plate current."



    "WELL, I hope that the boys know what you're talking about," interrupted Mr. Layton at this point, his eyes twinkling, "for I'm sure I don't."
    "They know what I'm talking about all right," returned his guest, admiration in his laughing eyes as he looked at the boys. "Unless I miss my guess, these fellows are the stuff of which radio experts are made. I bet they'll do great things yet."
    "Won't you tell us more about your experiences?" begged Herb, while the other boys tried not to look too pleased at the praise. "It isn't often we have a chance to hear of adventures like yours first hand."
    "Well," said Mr. Bentley, modestly, "I don't know that there's much to tell. All we scouts do is to patrol the country and watch for fires. Of course, in case of a big fire, our duties are more exciting. I remember one fire," he leaned back in his chair reminiscently and the boys listened eagerly, hanging on every word. "It was a beauty of its kind, covering pretty nearly fourteen miles. Thousands of dollars' worth of valuable timber was menaced. It looked for a time as if it would get the better of us, at that.
    "Men were scarce and there was a high wind to urge the fire on. A receiving set was rushed to the fire line, some of the apparatus in a truck and some carried by truck horses. My plane was detailed to patrol the fire line and give directions to the men who were fighting the fire."
    He paused, and the boys waited impatiently for him to go on.
    "The good old plane was equipped for both sending and receiving, and I tell you we patrolled that fourteen miles of flaming forest, sometimes coming so close to the tree tops that we almost seemed to brush them.
    "My duty, of course, was to report the progress of the fire. Controlled at one point, it broke out at another, and it was through the messages from my 'plane to the ground set stationed just behind the fire line that the men were moved from one danger point to the next.
    "Finally, the fire seeming nearly out along one side of the ridge, I sent the men to fighting it on the other side, where it had been left to rage uncontrolled. No sooner had the men scattered for the danger point than the brooding fire broke out again and it was necessary to recall half the men.
    "It was a long fight and a hard one, but with the aid of the blessed old wireless, we finally won out. As a matter of fact, the wireless-equipped airplane has become as necessary to the Forest Service as ships are to the navy.
    "In the old days," he went on, seeing that the boys were still deeply interested, "when they depended upon the ordinary telephone to convey warnings of fires they were surely leaning upon a broken reed.
    "Often, just when they needed the means of communication most, the fire would sweep through the woods, destroying trees to which the telephone wires were fastened, and melting the wires themselves. So the eyes of the Forest Service were put out and they were forced to work in the dark."
    "But I should think," protested Bob, "that there would be times when even wireless would be put out of the job. Suppose the fire were to reach one of the stations equipped with wireless. What then?"
    Mr. Bentley laughed as though amused at something.
    "I can tell you an interesting incident connected with that," he said. "And one that shows the pluck and common sense of radio operators in general--don't think that I'm throwing bouquets at myself, flow, for first and last, I am a pilot, even if sometimes I find it necessary to employ radio.
    "Well, anyway, this operator that I am speaking of, found himself in a perilous position. A fire had been raging for days, and flow it was so close to his station that the station itself was threatened.
    "One morning when he got up the smoke from the burning forest was swirling about the open space in front of the station and he knew that before long he would be seeing flame instead of smoke. The fire fighters had been working ceaselessly, fighting gallantly, but the elements were against them. The air was almost as dry and brittle as the wood which the flames lapped up and there was a steady wind that drove the fire on and on.
    "If only there might come a fog or the wind change its direction! But the radio man had no intention of waiting on the elements. I don't believe he gave more than a passing thought to his own safety--his chief interest was for the safety of his beloved apparatus.
    "He decided to dismantle the set, build a raft and set himself and the apparatus adrift upon the water in the attempt to save it.
    And so he worked feverishly, while the fire came closer and he could hear the men who were fighting the fire shouting to each other. Finally he succeeded in dismantling the set and got it down to the water's edge.
    "Here he built a rough raft, piled the apparatus upon it, jumped after it, and drifted out into the middle of the lake."
    "Did the station burn down?" asked Jimmy excitedly.
    "No, fortunately. The wind died down in the nick of time, giving the men a chance to control the blaze. When it was evident the danger was past, the operator set up his apparatus again and prepared to continue his duties, as though nothing had happened.
    "There you have the tremendous advantage of radio. There were no wires to be destroyed. Only a radio set which could be dismantled and taken to safety while the fire raged."
    "That operator sure had his nerve with him, all right," said Bob admiringly.
    "More nerve than common sense perhaps," chuckled Mr. Bentley. "But you certainly can't help admiring him. He was right there when it came to grit."
    After a while they began to discuss technicalities, and the boys learned a great many things they had never known before. The pilot happening to mention that there were sometimes a number of airplanes equipped with radio operating within a restricted district, Joe wanted to know if they did not have a good deal of trouble with interference.
    "No. There was at first some interference by amateurs, but these soon learned to refrain from using their instruments during patrol periods.
    "You see," he explained, "we use a special type of transmitting outfit aboard our fire-detection craft. It's called the SCR-Seventy-three. The equipment obtains its power from a self-excited inductor type alternator. This is propelled by a fixed wooden-blade air fan. In the steamline casing of the alternator the rotary spark gap, alternator, potential transformer, condenser and oscillation transformer are self-contained. Usually the alternator is mounted on the underside of the fuselage where the propeller spends its force in the form of an air stream. The telegraph sending keys, field and battery switch, dry battery, variometer and antenna reel are the only units included inside the fuselage.
    "The type of transmitter is a simple rotary gap, indirectly excited spark and provided with nine taps on the inductance coil of the closed oscillating circuit. Five varying toothed discs for the rotary spark gap yield five different signal tones and nine different wave lengths are possible.
    "So," he finished, looking around at their absorbed faces, "you see it is quite possible to press into service a number of airplanes without being bothered by interference."
    "It sounds complete," said Bob. "I'd like a chance to see one of those sets at close range sometime."
    The time passed so quickly that finally the visitor, rose with an apology for staying so late. The radio boys were sorry to see him go. They could have sat for hours more, listening to him.
    "That fellow sure has had some experiences!" said Joe, as, a little later, the boys mounted the stairs to Bob's room. "It was mighty lucky we happened along while he was here."
    "You bet your life," said Herb. "I wouldn't have missed meeting him for a lot."
    "Say, fellows," Jimmy announced from the head of the stairs, "I know now what I'm going to do when I'm through school. It's me for the tall timber. I'm going to pilot an airplane in the service of my country."
    "Ain't he noble?" demanded Herb, grinning, as the boys crowded into Bob's room.



    SEVERAL days later while the radio boys were experimenting with their big set and talking over their interesting meeting with the Forest Service ranger, Herb displayed an immense horseshoe magnet.
    "Look what he's got for luck," chortled Jimmy. "The superstitious nut!"
    "Superstitious nothing!" snorted Herb. "If I'd wanted it for luck I wouldn't have got a magnet, would I? Any old common horseshoe would have done for luck."
    "Well, what's the big idea?" asked Bob, looking up from the audion tube he was experimenting with. "Or is there any?" he added, with a grin.
    "You bet your life there is!" returned Herb. "It's got to do with that very audion tube you're fussing with."
    "Ah, go on," jeered Joe, good-naturedly. "What's a magnet got to do with an audion tube, I'd like to know!"
    "Poor old Herb," added Jimmy, with a commiserating shake of the head.
    "Say, look here, all you fellows! Don't you go wasting any pity on me," cried Herb hotly. "If you don't look out, I won't show you my experiment all."
    "Go on, Herb," said Bob consolingly. "I'm listening."
    "Well, I'm glad there's one sensible member of this bunch!" cried Herb, and from then on addressed himself solely to Bob. "Look here," he said. "You can make the audion tube ever so much more sensitive to vibration if you put this magnet near it."
    "Who says so?" asked Bob, with interest.
    "I do. Here, put on the headphones and listen. I'll prove it to you."
    Bob obeyed and tuned in to the nearest broadcasting station where a concert was scheduled. As soon as he signified by a nod of his head that the connection was satisfactory Herb placed the big horseshoe magnet in such a position that the poles of the magnet were on each side of the tube. Sure enough, Bob was amazed at the almost magical improvement in the sound. It was clearer, more distinct, altogether more satisfactory. He listened in for another moment then wonderingly took off the headphones while Herb grinned at him in triumph.
    "Well, what do you think?" asked the latter while Joe and Jimmy looked at them curiously.
    "Think?" repeated Bob, still wonderingly. "Why, there's only one thing to think, course. That fool horseshoe of yours, Herb, is one wonderful improvement. I don't know how it works, but it surely is a marvel."
    Herb glanced at Jimmy and Joe in triumph.
    "What did I tell you?" he said. "Perhaps now you'll believe that my idea wasn't such a fool one after all."
    "But what did it do, Bob?" asked Joe, mystified.
    "It increased the sensitivity of that old audion tube, that's what it did," replied Bob, absently, his mind already busy with inventive thoughts. "I can't see yet just how it accomplished it, but the connection with the station was certainly clearer and more distinct than usual."
    "But how can a magnet increase the sensitivity of a vacuum tube?" asked Jimmy, not yet wholly convinced. "It doesn't make sense."
    "Well, don't see why not," contradicted Joe slowly. "I suppose the improvement is due to the magnetic effect of the magnet upon the electrons flowing from the filament to the plate. I don't exactly see why it should be an improvement, but if it is, then there must be some reason for it."
    "I wish we could find the reason!" cried Bob excitedly. "If we could make some improvement upon the vacuum tube----"
    "Don't wake him up, he is dreaming!" cried Herb. "If you don't look out, old boy, you'll have us all millionaires."
    "Well, there are worse things," retorted Bob, taking the magnet from Herb's hand and placing it near the tube. "This has given us something to think about, anyway."
    For a while they puzzled over the mystery, trying to find some way in which the discovery might be made to serve a practical purpose--all except Herb, who retired to one corner of the "lab" to fuss with some chemicals which he fondly hoped might be used in the construction of a battery.
    So engrossed were the boys in the problem of the magnet and vacuum tube that they forgot all about Herb and his experiments. So what happened took them completely off their guard.
    There was a sudden cry from Herb, followed closely by an explosion that knocked them off their feet. For a moment they lay there, a bit dazed by the shock. Then they scrambled to their feet and looked about them. Herb, being the nearest to the explosion, had got the worst of it. His face and hands were black and he was shaking a little from the shock. He gazed at the boys sheepishly.
    "Wh-what happened?" asked Jimmy dazedly. "An earthquake, I guess," replied Bob, as he looked about him to see what damage had been done.
    "Say, what's the big idea, anyway," Joe demanded of the blackened Herb. "Trying to start a Fourth of July celebration, or something?"
    "I was just mixing some chemicals, and the result was a flare-up," explained Herb sulkily. "Now, stop rubbing it into a fellow, will you? You might know I didn't do it on purpose."
    Bob began to laugh.
    "Better get in connection with some soap and water, Herb," he said. "Just now you look like the lead for a minstrel show."
    "Never mind, Herb," Joe flung after the disconsolate scientist as he made for the door. "As long as you don't hurt anything but Jimmy's doughnuts, we don't care. You can have as many explosions as you like."
    "Just the same," said Bob soberly, as they returned to the problem of the vacuum tube, "we're mighty lucky to have come off with so little damage. Mixing chemicals is a pretty dangerous business unless you know just what you're doing."
    "And even then it is," added Joe.



    THE days passed by, the boys becoming more and more engrossed in the fascination of radio all the time. They continued to work on their sets, sometimes with the most gratifying results, at others seeming to make little headway.
    But in spite of occasional discouragements they worked on, cheered by the knowledge that they were making steady, if sometimes slow, progress.
    There were so many really worth-while improvements being perfected each day that they really found it difficult to keep up with them all.
    It was about that time that Bob found out about Adam McNulty. Adam McNulty was the blind father of the washerwoman who served the four families of the boys.
    Bob went to the McNulty cabin, buried in the most squalid district of the town, bearing a message from his mother. When he got there he found that Mr. McNulty was the only one at home.
    The old fellow, smoking a black pipe in the bare kitchen of the house, seemed so pathetically glad to see some one--or, rather, to hear some one--that Bob yielded to his invitation to sit down and talk to him.
    And, someway, even after Bob reached home, he could not shake off the memory of the lonesome old blind man with nothing to do all day long but sit in a chair smoking his pipe, waiting for some chance word from a passer-by.
    It did not seem fair that he, Bob, should have all the good things of life while that old man should have nothing--nothing, at all.
    He spoke to his chums about it, but, though they were sympathetic, they did not see anything they could do.
    "We can't give him back his eyesight, you know," said Joe absently, already deep in a new scheme of improvement for the set.
    "No," said Bob. "But we might give him something that would do nearly as well."
    "What do you mean?" they asked, puzzled. "Radio," said Bob, and laid his hand lovingly on the apparatus. "If it means a lot to us, just think how much more it would mean to some one who hasn't a thing to do all day but sit and think. Why, I don't suppose any of us who can see can begin to realize what it would mean not to be able even to read the daily newspaper."
    The others stared at Bob, and slowly his meaning sank home.
    "I get you," said Joe slowly. "And say, let me tell you, it's a great idea, Bob. It wouldn't be so bad to be blind if you could have the daily news read to you every day----"
    "And listen to the latest on crops," added Jimmy.
    "To say nothing of the latest jazz," finished Herb, with a grin.
    "Well, why doesn't this blind man get him self a set?" asked Jimmy practically. "I should think every blind person in the country would want to own one."
    "I suppose every one of them does," said Bob. "And Doctor Dale said the other day that he thought the time would come when charities for the blind would install radio as a matter of humanity, and that prices of individual sets would be so low that all the blind could afford them. The blind are many of them old, you know, and pretty poor."
    "You mean," said Herb slowly, "that most of the blind folks who really need radio more than anybody else can't afford it? Say, that doesn't seem fair, does it?"
    "It isn't fair!" cried Bob, adding, eagerly: "I tell you what I thought we could do. There's that old set of mine! It doesn't seem much to us now, beside our big one, but I bet that McNulty would think it was a gold mine."
    "Hooray for Bob!" cried Herb irrepressibly. "Once in a while he really does get a good idea in his head. When do we start installing this set in the McNulty mansion, boys?"
    "As soon as you like," answered Bob. "Tomorrow's Saturday, so we could start early in the morning. It will probably take us some time to rig up the antenna."
    The boys were enthusiastic about the idea, and they wasted no time putting it into execution. That very night they looked up the old set, examining it to make sure it was in working order.
    When they told their families what they proposed to do, their parents were greatly pleased.
    "It does my heart good," said Mr. Layton to his wife, after Bob had gone up to bed, "to see that those boys are interested in making some one besides themselves happy."
    "They're going to make fine men, some day," answered Mrs. Layton softly.
    The boys arrived at the McNulty cottage so early the next morning that they met Maggie McNulty on her way to collect the day's wash.
    When they told her what they were going to do she was at first too astonished to speak and then threatened to fall upon their necks in her gratitude.
    "Shure, if ye can bring some sunshine into my poor old father's dark life," she told them in her rich brogue, tears in her eyes, "then ye'll shure win the undyin' gratitude uv Maggie McNulty."
    It was a whole day's job, and the boys worked steadily, only stopping long enough to rush home for a bit of lunch.
    They had tried to explain what they were doing to Adam McNulty, but the old man seemed almost childishly mystified. It was with a feeling of dismay that the boys realized that, in all probability, this was the first time the blind man had ever heard the word radio. It seemed incredible to them that there could be anybody in the world who did not know about radio.
    However, if Adam McNulty was mystified, he was also delightedly, pitifully excited. He followed the boys out to the cluttered back yard where they were rigging up the aerial, listening eagerly to their chatter and putting in a funny word now and then that made them roar with laughter.
    Bob brought him an empty soap box for a seat and there the old man sat hour after hour, despite the fact that there was a chill in the air, blissfully happy in their companionship. He had been made to understand that something pleasant was being done for him, but it is doubtful if he could have asked for any greater happiness than just to sit there with somebody to talk to and crack his jokes with.
    They were good jokes too, full of real Irish wit, and long before the set was ready for action the boys had become fond of the old fellow.
    "He's a dead game sport," Joe said to Bob, in that brief interval when they had raced home for lunch. "I bet I'd be a regular old crab, blind like that."
    Mrs. Layton put up an appetizing lunch for the blind man, topping it off with a delicious homemade lemon pie and a thermos bottle full of steaming coffee.
    The way the old man ate that food was amazing even to Jimmy. Maggie was too busy earning enough to keep them alive to bother much with dainties. At any rate, Adam ate the entire lemon pie, not leaving so much as a crumb.
    "I thought I was pretty good on feeding," whispered Joe, in a delighted aside, "but I never could go that old bird. He's got me beat a mile."
    "Well," said Jimmy complacently, "I bet I'd tie with him."
    If the boys had wanted any reward for that day of strenuous work, they would have had it when, placing the earphones upon his white head, they watched the expression of McNulty's face change from mystification to wonder, then to beatific enjoyment.
    He listened motionless while the exquisite music flooded his starved old soul. Toward the end he closed his eyes and tears trickled from beneath the lids down his wrinkled face. He brushed them off impatiently and the boys noticed that his hand was trembling.
    It was a long, long time before he seemed to be aware that there was any one in the room with him. He seemed to have completely forgotten the boys who had bestowed this rare gift upon him.
    After a while, coming out of his dream, the old man began fumbling with the headphones as if he wanted to take them off, and Bob helped him. The man tried to speak, but made hard work of it. Emotion choked him.
    "Shure, an' I don't know what to make of it at all, at all," he said at last, in a quivering voice. "Shure an' I thought the age of miracles was passed. I'm only an ignorant old man, with no eyes at all; but you lads have given me something that's near as good. Shure an' it's an old sinner I am, for shure. Many's the day I've sat here, prayin' the Lord would give me wan more minute o' sight before I died, an' it was unanswered my prayers wuz, I thought. It's grateful I am to yez, lads. It's old Adam McNulty's blessin' ye'll always have. An' now will yez put them things in my ears? It's heaven's own angels I'd like to be hearin' agin. That's the lad--ah!"
    And while the beatific expression stole once more over his blind old face the boys stole silently out.



    THE boys saw a good deal of Adam McNulty in the days that followed, and the change in the old man was nothing short of miraculous.
    He no longer sat in the bare kitchen rocking and smoking his pipe, dependent upon some passer-by for his sole amusement. He had radio now, and under the instruction of the boys he had become quite expert in managing the apparatus. Although he had no eyes, his fingers were extraordinarily sensitive and they soon learned to handle the set intelligently.
    His daughter Maggie, whose gratitude to the boys knew no bounds, looked up the radio program in the paper each day and carefully instructed her father as to just when the news reports were given out, the story reading, concerts, and so forth.
    And so the old blind man lived in a new world--or rather, the old world which he had ceased to live in when he became blind--and he seemed actually to grow younger day by day. For radio had become his eyes.
    Doctor Dale heard of this act of kindness on the part of the boys and he was warm in his praise.
    "Radio," he told the boys one day when he met them on the street, "is a wonderful thing for those of us that can see, but for the blind it is a miracle. You boys have done an admirable thing in your kindness to Adam McNulty, and I hope that, not only individuals, but the government itself will see the possibilities of so great a charity and follow your example."
    The boys glowed with pride at the doctor's praise, and then and there made the resolve that whenever they came across a blind person that person should immediately possess a radio set if it lay within their power to give it to him.
    On this particular day when so many things happened the boys were walking down Main Street, talking as usual of their sets and the marvelous progress of radio.
    "What you thinking about, Bob?" asked Joe, noticing that his chum had been quiet for some time.
    "I was thinking," said Bob, coming out of his reverie, "of the difference there has been in generators since the early days of Marconi's spark coil. First we had the spark transmitters and then we graduated to transformers."
    "And they still gave us the spark," added Joe, taking up the theme. "Then came the rotary spark gap and later the Goldsmith generator."
    "And then," Jimmy continued cheerfully, "the Goldsmith generator was knocked into a cocked hat by the Alexanderson generator."
    "They'll have an improvement on that before long, too," prophesied Herb.
    "They have already," Bob took him up quickly. "Don't you remember what Doctor Dale told us of the new power vacuum tube where one tube can take care of fifty K. W.?"
    "Gee," breathed Herb admiringly, "I'll say that's some energy."
    "Those same vacuum tubes are being built right now," went on Bob enthusiastically. "They are made of quartz and are much cheaper than the alternators we're using now."
    "They are small too, compared to our present-day generators," added Joe.
    "You bet!" agreed Bob, adding, as his eyes narrowed dreamily: "All the apparatus seems to be growing smaller these days, anyway. I bet before we fellows are twenty years older, engineers will have done away altogether with large power plants and cumbersome machinery."
    "I read the other day," said Joe, "that before long all the apparatus needed, even for trans-atlantic stations, can be contained in a small room about twenty-five feet by twenty-five."
    "But what shall we do for power?" protested Herb. "We'll always have to have generators."
    "There isn't any such word as 'always' in radio," returned Bob. "I shouldn't wonder if in the next twenty or thirty years we shall be able, by means of appliances like this new power vacuum tube, to get our power from the ordinary lighting circuit."
    "And that would do away entirely with generators," added Joe triumphantly.
    "Well, I wouldn't say anything was impossible," said Herb doubtfully. "But that seems to me like a pretty large order."
    "It is a large order," agreed Bob, adding with conviction: "But it isn't too large for radio to fill."
    "Speaking of lodging all apparatus in one fair-sized room," Joe went on. "I don't see why that can't really be done in a few years. Why, they say that this new power vacuum tube which handles fifty K. W. is not any larger than a desk drawer."
    "I see the day of the vest-pocket radio set coming nearer and nearer, according to you fellows," announced Herb. "Pretty soon we'll be getting our apparatus so small we'll need a microscope to see it."
    "Laugh if you want to," said Bob. "But I bet in the next few years we're going to see greater things done in radio than have been accomplished yet."
    "And that's saying something!" exclaimed Joe, with a laugh.
    "I guess," said Jimmy thoughtfully, "that there have been more changes in a short time in radio than in any other science.
    "I should say so!" Herb took him up. "Look at telephone and telegraph and electric lighting systems. There have been changes in them, of course, but beside the rapid-fire changes of radio, they seem to have been standing still."
    "There haven't been any changes to speak of in the electric lighting systems for the last fifteen years or more," said Bob. "And the telephone has stayed just about the same, too."
    "There's no doubt about it," said Joe. "Radio has got 'em all beat as far as a field for experiment is concerned. Say," he added fervently, "aren't you glad you weren't born a hundred years ago?"
    The boys stopped in at Adam McNulty's cabin to see how the old fellow was getting along. They found him in the best of spirits and, after "listening in" with him for a while and laughing at some of his Irish jokes, they started toward home.
Pages 117-121:

    At last the lunch came to an end and Mr. Brandon professed himself ready to talk shop.
    He was enthusiastic over the radio set the boys showed him and declared that he could see very little improvement to suggest.
    "You surely have kept up with the march," he said admiringly. "You have pretty nearly all the latest appliances, haven't you? Good work, boys. Keep it up and you'll be experts in earnest."
    "If we could only find some way to lengthen the life of our storage batteries," said Bob, not without a pardonable touch of pride, "we wouldn't have much to complain about. But that battery does puzzle us."
    "Keep your battery filled with water and see if it doesn't last you about twice as long," suggested the radio expert. "Don't add any acid to your battery, for it's only the water that evaporates."
    "Will that really do the trick?" asked Joe, wondering. "I don't just see how----"
    "It does just the same," Brandon interrupted confidently. "All you have to do is to try it to find out. Don't use ordinary water though. It needs to be distilled."
    "That's a new one on me, all right," said Bob, adding gratefully: "But we're obliged for the information. If distilled water will lengthen the life of our battery, then distilled water it shall have."
    "It seems queer," said Mr. Brandon reflectively, "how apparently simple things will work immense improvement. Marconi, for instance, by merely shortening his wave length, is discovering wonderful things. We cannot even begin to calculate what marvelous things are in store for us when we begin to send out radio waves of a few centimeters, perhaps less. We have not yet explored the low wave lengths, and when we do I believe we are in for some great surprises."
    "Go on," said Joe, as he paused. "Tell us more about these low wave lengths."



    FRANK BRANDON shook his head and smiled.
    "I'm afraid I don't know much more to tell," he said. "As I have said, what will happen when we materially decrease the wave length, is still in the land of conjecture. But I tell you," he added, with sudden enthusiasm, "I'm mighty glad to be living in this good old age. What we have already seen accomplished is nothing to what we are going to see. Why," he added, "some scientists, Steinmetz, for instance, are even beginning to claim that ether isn't the real medium for the propagation of radio waves."
    "What do you mean by that?" asked Bob, with interest. "Is it some sort of joke?"
    "Joke, nothing!" replied Frank Brandon. "As. a matter of fact, I fully believe that electro-magnetic waves can as easily be hurled through a void as through ether."
    The boys were silent for a moment, thinking this over. It sounded revolutionary, but they had great respect for Frank Brandon's judgment.
    "There's the Rogers underground aerial," Bob suggested tentatively, and Brandon took him up quickly.
    "Exactly!" he said. "That leans in the direction of what I say. Why, I believe the day is coming--and it isn't so very far in the future, either--when no aerial will be used.
    "Why, I believe," he added, becoming more and more enthusiastic as he continued, "that ten years from now we shall simply attach our receiving outfits to the ground and shall be able to receive even more satisfactorily than we do to-day." He laughed and added lightly:
    "But who am I to assume the rôle of prophet? Perhaps, like a good many prophets, I see too much in the future that never will come true."
    "I don't believe it," said Bob. "I shouldn't wonder if all you prophesy will come true in a few years."
    "Well," said Herb, with a grin, "it will be a relief not to get any more broken shins putting up aerials."
    Mr. Brandon laughed.
    "I'm with you," he said. "I've been there myself."
    "Have you read about that radio-controlled tank?" Joe asked. "The one that was exhibited in Dayton, I mean?"
    "I not only read about it, I saw it," Mr. Brandon answered, and the boys stared at him in surprise. "I happened to be there on business," he said; "and you can better believe I was on hand when they rolled that tank through the traffic."
    "What did it look like?" asked Jimmy eagerly. "The car was about eight feet long and three feet high," responded Brandon. "It was furnished with a motor and storage batteries, and I guess its speed was about five or six miles an hour."
    "And was it really controlled by radio?" put in Herb, wishing that he had been on the spot.
    "Absolutely," returned Brandon. "An automobile followed along behind it and controlled it entirely by wireless signals. The apparatus that does all the work is called the selector, and it's only about the size of a saucer. It decodes the dots and dashes and obeys the command in an inconceivably short time--about a quarter of a second."
    "It can be controlled by an airplane, too, can't it?" asked Bob, and the radio inspector nodded.
    "In case of war," he said slowly, "I imagine these airplane-controlled tanks could do considerable damage."
man receiving a message Pages 172-176:

    "Just before you arrived I was considering the advisability of putting the matter into the hands of the police," said Mr. Fennington. "What would you do ?"
    "Keep the whole thing to ourselves for the present," said Mr. Brandon decisively. "I'll send for a couple of good men to come up here and help me, and we'll keep a watch on that cabin for a few days. If this thing got into the papers, it would put the crooks on their guard, and probably spoil our chances of catching them and getting back the loot. I've got a small but extremely efficient receiving and sending set in my car, and if any more code messages are sent out we'll catch them."
    His confidence was contagious, and the boys felt almost as though the capture of the criminals had already been accomplished.
    "What puzzles me, though," remarked Mr. Fennington, "is how you knew that there was an unauthorized radio sending station in this neighborhood, Mr. Brandon. I should think it would be almost impossible to locate such a station, even approximately."
    "On the contrary," replied Frank Brandon, "it is little more than a matter of routine. Probably any of these radio fiends here could explain the method as well as I can, but I'll try to make it plain to you.
    "There is a certain type of aerial that has what we call 'directional' properties, that is, when it is shifted around, the incoming signals will be loudest when this loop aerial, as it is called, is directly in line with the sending station. The receiving antenna is wound on a square frame, and when the signals are received at their maximum strength, we know that the frame is in a practically straight line with the sending station we're after."
    "Yes, but that still leaves you in the dark as to whether the station is one mile away or a hundred miles," observed Mr. Fennington, as Brandon paused.
    "That's very true," answered the other. "And for that reason we can't stop at using just one loop aerial. What we actually do is to have three stations, each one equipped with a loop. These three stations are located a good many miles apart. Now, with these three loops, we have three lines of direction. We lay out these lines on a chart of the territory, and where they intersect, is the place where the unlicensed station is located. Is that clear?"
    "Perfectly," said Mr. Fennington. "But what looks like a point on the map may be a large space on the actual territory."
    "Oh, yes, our work isn't done by any means after we have got our first rough bearings," continued Brandon. "Having determined the approximate position, we take the loops and receivers to what we know is a place quite near the station we're after, and then we repeat the former process. This time it is much more accurate. Gradually we draw the net tighter until we find the antenna belonging to the offender, and then--well, we make him wish he hadn't tried to fool the government."
    "You certainly have it reduced to an exact science," acknowledged Mr. Fennington. "I don't wonder that everybody interested in radio gets to be a fanatic."
    "We'll make a 'bug' out of you before we get through, Dad," declared Herb, grinning.
    "If my load of silk is recovered through the agency of radio, I'll be enthusiastic enough over it to suit even you fellows," said his father. "It will mean the best set that money can buy for you if I get it back."
    "We'll hold you to that promise," threatened Herb. "Radio can do anything," he added, with the conviction of a devotee.
    "Well, pretty nearly everything," qualified Mr. Brandon. "A little while ago it was considered marvelous that we could transmit the voice by radio, and now the transmission of photographs by radio has been successfully accomplished."
    "What!" exclaimed Mr. Fennington incredulously. "Do you mean to say that an actual recognizable photograph has been sent through the air by radio? That seems almost too much to believe."
    "Nevertheless, it has been done," insisted Frank Brandon. "I saw the actual reproduction of one that had been sent from Italy to New York by the wireless route, and while I can't claim that it was perfect, still it was as plain as the average newspaper picture. And don't forget that this is a new phase of the game, and is not past the experimental stage yet."
    "Well, after that, I am inclined to agree with Herbert that 'radio can do anything, " admitted Mr. Fennington.
    "I don't think we'll have much trouble making a convert of you," laughed the radio inspector. "No doubt the quickest way, though, will be to recover your stolen shipment, so we'll start working in that direction the first thing in the morning."
    And in this he was as good as his word. He was up betimes, getting in touch with headquarters by means of his compact portable outfit. He kept at work until he had received the promise of two trustworthy men, who were to report to him at the lumber camp as soon as they could get there. Then he routed out the radio boys, and after a hasty breakfast they all set out to locate the cabin where the boys had found the code key.