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Navigation is the process by which a ship (or other vehicle) gets from one place to another. The process requires planning, recording, and controlling the movement of the ship. An essential attribute is being able to calculate ones position. This requires a variety of increasing sophisticated techniques, including dead reckoning, piloting, and celestial navigation. (Modern navigation is based on positions established by electronic data from satellites.)

By the time that Jack Aubrey takes command of the Surprise in 1800, most of the tools and techniques for successful navigation were developed, particularly where the fleets of the period operated. The compass provided general direction for travel and wind although magnetic variation as the cause of inaccuracy was not fully understood.[1] Charts, in large measure were more or less reliable and becoming more detailed as navies rushed to produce detailed records of their new territories . Distance was measured by log whose margin of error for dead reckoning was insignificant in relation to the stately ship speeds. Latitude as a measure and device was solved, and its increasing precision was the product of better tools culminating in the sextant, more or less in its final form in about 1730. The Nautical almanac first published in 1767, provided the data to facilitate celestial navigation. The position of Longitude, had long been problematic and resolved only by the most complex of complications comparing the position of the moon relative to stars, known as lunars. Longitude too was finally solved with Harrison's chronometer as established by Cook's circumnavigation of 1779. Readily available accurate time pieces solved longitude.

Nonetheless the knowledge, its skillful application and the tools were variously available to ships though out the period. In addition long periods of bad weather could make precise celestial navigation impossible leaving the ultimate safety of the ship to dead reckoning and seamanship. All mariners were most conscious of the potential dangers, particularly when closing with land. All British sailors would have known the fate of Sir Cloudesley Shovell's fleet which he drove onto the rocks of the Scilly isles by mis-judging his actual position.

Patrick O'Brian reflects these concerns and realities in the novels of the Aubreyad. Jack Aubrey's navigational concerns are indicative of his role and responsibilities and are one aspect that provides the novels historical texture and content. Patrick O'Brian as a creative author also uses these concerns to develop characters, plot, context and lyricism. To paraphrase Freud, sometimes Saturn is just Saturn, and a means to provide navigational context; at other times O'Brian's celestial objects are much much more.


  1. C.f., Aubrey's comments re. the soundings he had taken of St. Martin's "during the year ninety-seven: 'the variation of the compass had altered thirty-one seconds eastwards since then and some of the soundings would need revision'". O'Brian, Patrick. The Letter of Marque. (c)1988 by Patrick O'Brian. First American Edition, 1990. W.W. Norton & Company, Inc. New York, NY: p. 136
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