Dear All, The question that Gary originally raised regarding an aeroplane leaving O'Hare, and which Rob answered, certainly to my satisfaction, is turning into a very interesting point. If the atmosphere is rotating en mass with the World, and winds spring up all over the place, in almost random directions, then what is it that acts upon the molecules in those winds, in order to bring them back into eastwardly, differential rotation with the World? If it were the pressure exerted by other air molecules, then in a very short timespan the atmosphere, as a whole, would slow down and stop. Neville. --------------------------------- ALL-NEW Yahoo! Messenger - all new features - even more fun!