Up and up Hal pushed his rough-built, patched-winged old army relic, reveling wildly in the freedom of the skies, fourteen, fifteen, sixteen thousand feet up. Intense cold froze him to the marrow, chattered his teeth. Air pressure weighted his brain, reeled his head dizzily. If only he had some protecting, oxygen-piped helmet to protect him from air heights, as a diver had helmet to save him from water pressure! If--if! Then he could explore the great unknown of the air! But even at a puny sixteen-thousand-foot height, the sky had revelations for one that soared its spaces knowingly.