* * * * * The two searchers had emerged upon a wide gallery that commanded a clear view of the main entrance where various specimens of American fauna were mounted in intriguing replicas of their native habitat. The guard pointed an accusing finger at one of these groups and sprang toward the stairs. The old gentleman's breath and strength were gone. He could only gaze in the direction that had been indicated by the madly running guard; but he had no doubts. A small boy was certainly digging vigorously at the head of a specimen of _Ursus Polaris_ that the curator had represented in the dramatic pose of killing a seal. A protesting wail arose from below as the young naturalist was withdrawn from his field by a capable hand on the slack of his trousers. And presently, chagrined with failure, the culprit was before his grandsire. "Gee!" he complained, "I was only looking at the polar bear. Are polar bears always white? Are--" "You'd better take him away, sir," interrupted the sergeant. "He was trying to pry out one of the bear's eyes with the stick of the lollypop I give him. Take him." The old gentleman extended both hands. His left found a grip in his grandson's coat collar; his right, partly concealing a government engraving, met the guard's with a clasp of gratitude. "Sergeant," he remarked in a voice tense with feeling, "a half-hour ago I expressed some ridiculous regrets that Drayle's invention had been kept from the world. Now I realize its horrid menace. I shudder to think it might have been responsible for two like him!" The object of disapproval was shaken indicatively. "Guard the secret well, Sergeant! Guard it well! The world's peace depends upon you!" The old gentleman's words trembled with conviction. Then alternately shaking his head and his grandson he marched down the hallway, ebony cane tapping angrily upon the stone. As the exhausted but happy warrior retraced his steps a high-pitched voice floated after him. "Grandpa, are polar bears _always_ white?" * * * * * [Advertisement: ] The Reader's Corner _A Meeting Place for Readers of_ Astounding Stories [Illustration: _The Reader's Corner_] _The Invisible X-Flyers_ The following is a semi-technical description of the operation of the invisible X-flyers used in "Jetta of the Lowlands" as compiled by Philip Grant in the year 2021 from official records of the Anti-War Department of the United States of North America, and discovered recently by Ray Cummings.