This paper was presented by the Executive Secretary at the twentieth anniversary convention of the Australian Institute of Navigation held in Sydney, New South Wales, on 10 and 11 October 1969.In July this year two men landed on the Moon, certainly the most spectacular navigational achievement of mankind. It was a voyage backed by all the massive scientific resources of a modern industrial state, in which thousands of people were directly involved. The astronauts were a single link in a navigational loop employing a host of technologies.Two hundred years previously James Cook had sailed on the first of his three great voyages, during which he discovered New Zealand and the coast of New South Wales. Cook was perhaps the most illustrious navigator of all times, even if perhaps he advanced the art more by force of character than by any specific contribution. When he started his voyages, the art of nautical astronomy was in its infancy. At their finish William Wales could comment, in 1788, that no officer who had been concerned with them ‘would not, whatever his real skill may be, feel ashamed to have it thought that he did not know how to observe for and compute the time at sea, though but a short time before these voyages…such a thing was scarcely ever heard of among seamen; and even first-rate astronomers doubted the probability of doing it with sufficient exactness’.