NAVIGATION n.
Ships in general. [Poetic] Shak. Aërial navigation, the act or art of sailing or floating in the air, as by means of ballons; aëronautic. -- Inland navigation, Internal navigation, navigation on rivers, inland lakes, etc.
RACK n.
Thin, flying, broken clouds, or any portion of floating vapor in the sky. Shak. The winds in the upper region, which move the clouds above, which we call the rack, . . . pass without noise. Bacon. And the night rack came rolling up. C. Kingsley.