Before writing _The Young Wireless Operator—As a Fire Patrol_, the writer spent many days in the forest with a District Forester, studying the actual working of the Pennsylvania State Forestry system, though in earlier years he had spent weeks camping and tramping in those same mountain forests. Many of the incidents used in the book were contributed by forest rangers. The manuscript of the book was read and approved by both the District Forester and Gifford Pinchot, then Pennsylvania Commissioner of Forestry and now Governor of Pennsylvania, in order that there might be no mistakes in the text. Mr. Pinchot also showed his approval of the book by writing a foreword for it. This present wireless series really had its inception, years ago, with the appearance of _In Camp at Fort Brady_. Readers of that book showed so much interest in some of the characters that, when it came to writing further volumes, the author naturally went on with the history of some of those boys. Thus Roy Mercer and Alec Cunningham and Charley Russell and Willie Brown, who have figured in _The Young Wireless Operator series_, are really old acquaintances, and made their first appearance in _In Camp at Fort Brady_, and their next in _The Secret Wireless_ and in _The Hidden Aerial_. The later volumes have dealt with individual members of the Camp Brady Wireless Patrol rather than with the Patrol as a whole. The author has become as much interested in this band of boys as he hopes any of his readers has. And it is his plan to go on with these individual histories until we know what became of each boy. Lewis Edwin Theiss. Otzinachson, Muncy, Pa. January 29, 1923. CONTENTS I. An Unexpected Opportunity II. An Adventure with a Secret Service Man III. A Tip by Wireless IV. The Capture of the Wool Smugglers V. On the Trail of a Cotton Thief VI. What Was Behind the False Partition VII. Willie Gets His Chance VIII. In the Armenian Quarter IX. Under a Cloud X. The Cloud Grows Darker XI. Willie Makes a Discovery XII. The Mystery of the Wheat Sacks XIII. Saved by Wireless XIV. Who Made the False Key? XV. A Watch on a Diamond Smuggler XVI. Where the Jewels Were Hidden XVII. After the Whiskey Smugglers XVIII. The Pursuit in the Dark XIX. Victory The Young Wireless Operator— With the U.S. Secret Service CHAPTER I AN UNEXPECTED OPPORTUNITY