As Hal Dane skimmed the ocean surface at a steady, rhythmic gait, his mind leaped ahead to future aircraft building that should utilize the knowledge that he had gained by his stratosphere explorations. He had found that the human body, fashioned to thrive in an air pressure of something over fourteen pounds per square inch, could suffer intensely when lifted to a rarefied air pressure of merely two and a half pounds to the inch. But since man had been smart enough to lift himself on wings above the clouds, why, now man must be smart enough to lift his normal air pressure with him. This could be done, Hal believed, by making the plane's cabin of metal, hermetically sealed, and equipped with oxygen tanks to maintain the same air pressure as at ordinary altitudes.