The United States Naval Observatory

摘要

<正> Sailors and pilots need three things to find their way: they musthave the correct time; they must know the exact position of the starsoverhead; and they must have a book that tells what the future positionof the stars will be. The information makes possible the science ofnavigation. And it is the job of the United States Naval Observatory tocollect and publish this information. The Headquarters of the Naval