Testing other people's inventions did not fill all of Hal's time. At nights, or whenever he could snatch a few hours to himself, he was forever pottering with pieces of fabric and metal and wood. Table top, dresser top, every available surface in his sleeping quarters seemed cluttered with aviation trash. Only not all of it was trash. Mixed in with wood shavings and screws and wire coils was a strange metal helmet, something like a diver's helmet, yet different,--light, graceful, not cumbersome in shape. A tube could be attached to the mouth-piece. Elsewhere in the litter sat a miniature oxygen tank. In these was expressed a forward thought for achievement in high flying. Little models of engines rubbed noses with wing models in various stages of incompleteness. Above a chifferobe was poised something that Hal Dane's eyes sought every time he entered his room--a completed model of a plane. It was a slim silver creation, all metal, and streamlined from engine, through monoplane wing, back to tail. Slender, yet with strength in every line! Smoke blown against this model did not eddy and swirl but slipped straight across her nonresistant lines. With her length of wing, she was built to ride the winds.