At this height, the air at ground level showed its true character. Alex could witness the organic filth in the low-lying atmosphere, banding the horizon all around him. It was a sepia-tinted permanent stain, a natural smog of dirts and grits and pollens, of molds and stinks and throat-clogging organic spew.... By contrast, the high sweet air around him now, cool and thin and irresistible, was a bone-washing galactic ether. He felt as if it were blowing straight through his flesh.