Crane sat in silence, his keen mind considering every aspect of the motions possible, of velocity, of acceleration, of inertia. He already knew well Seaton's resourcefulness in crises and his physical and mental strength. "As far as I can see, that might be safe," he admitted finally, "and we really should know something about it besides the theory." "Fine, Mart--let's get busy! I'll be ready in five minutes. Yell for the girls, will you? They'd break us off at the ankles if we pull anything new without letting them in on it." A few minutes later the "girls" strolled out into Crane Field, arms around each other--Dorothy Seaton, her gorgeous auburn hair framing violet eyes and vivid coloring; black-haired, dark-eyed Margaret Crane. "Br-r-r, it's cold!" Dorothy shivered, wrapping her coat more closely about her. "This must be the coldest day Washington has seen for years!" "It is cold," Margaret agreed. "I wonder what they are going to do out here, this kind of weather?" * * * * * As she spoke, the two men stepped out of the "testing shed"--the huge structure that housed their Osnomian-built space-cruiser, "Skylark II." Seaton waddled clumsily, wearing as he did a Crane vacuum-suit which, built of fur, canvas, metal and transparent silica, braced by steel netting and equipped with air-tanks and heaters, rendered its wearer independent of outside conditions of temperature and pressure. Outside this suit he wore a heavy harness of leather, buckled about his body, shoulders, and legs, attached to which were numerous knobs, switches, dials, bakelite cases, and other pieces of apparatus. Carried by a strong aluminum framework in turn supported by the harness, the universal bearing of a small power-bar rose directly above his grotesque-looking helmet. "What do you think you're going to do in that thing, Dickie?" Dorothy called. Then, knowing that he could not hear her voice, she turned to Crane. "What are you letting that precious husband of mine do now, Martin? He looks as though he were up to something." While she was speaking, Seaton had snapped the release of his face plate. "Nothing much, Dottie. Just going to show you-all the zone of force. Mart wouldn't let me turn it on, unless I got all cocked and primed for a year's journey into space." "Dot, what is that zone of force, anyway?" asked Margaret.