To an untrained ear the soft tappings would have sounded as vague and undefined as the footsteps of a fly on a sheet of sensitive matter. But to Jack, the whisperings winging their way in three hundred meter waves through space were as clear as a story read aloud. As he wrote, shoving his pencil over the sheets as fast as he could, Tom began to gasp. “Great ginger-snaps!” he choked out, and then, “Well, we were sighing for action, and it looks as if we’ll get it in big, juicy chunks before we’re much older.” While the message, destined to have such an important effect on their immediate future, is still pulsing through the air, we will take the opportunity to place the reader in closer touch, so to speak, with our two lads. Jack Chadwick, then, was the only son of Professor Chester Chadwick, an inventor, whose various discoveries in many mechanical fields had resulted in gaining him a handsome fortune. Jack’s mother had died when he was a tiny lad, and, as he was an only son, he had been brought up in constant association with his father. Almost as soon as he had mastered his earliest lessons Jack was familiar with his parent’s laboratory and workshop, and Mr. Chadwick, delighted at the interest the boy displayed in science, had made him a close companion. When Jack was twelve years old a new interest entered his life. His cousin, Tom Jesson, came to live with them at Mr. Chadwick’s handsome home on the outskirts of Boston. Tom was the son of Jasper Jesson, the noted traveler, and, like Jack, he was motherless. Mr. Jesson had, some time before, accepted a commission from a scientific institute to travel and collect antiquities in the then little-known territory of Yucatan. From this expedition he did not return within the year allotted him to complete his researches. Time went on and no word came from him, and at length he was given up for lost even by the most hopeful of his friends. And thus it was that his son Tom, then ten years old, came to High Towers, Mr. Chadwick’s estate, even then known as the home of a famous inventor. And so Jack and Tom had practically grown up together in close association and with kindred interests. To two lads of inventive mind, no more delightful field for their experiments could have been imagined than High Towers. A park of some fifty or sixty acres surrounded the house, which, among other features of a country estate, possessed a small lake. On this sheet of water Jack and Tom tried out models of a dozen different kinds of craft before they were fourteen. Professor Chadwick gave them practically “the run” of his workshops and experimental sheds, besides instructing them in scientific investigations.