'Ship's soul' still points the way

Victor Hugo remarked that the compass was "the soul of a ship". Anyone who has drifted in thick fog in a small boat would agree with him, as Alan Gurney obviously does. He recalls a 1998 incident when a yacht equipped with state-of-the-art electronic wizardry experienced a technological meltdown and was left with no compass to find her way home.

Gurney's story takes us back to the Greek and Roman worlds, where winds defined the cardinal directions. The first "compasses" were the seemingly magical lodestones, then the simple magnetised needles of 11th-century Chinese sailors and 12th-century European mariners.

Elizabethan scientist John Dee and other pioneers puzzled over variation and the wandering magnetic pole, culminating in the voyages of 17th-century scientist Edmond Halley, who became Astronomer Royal at Greenwich. He also produced the first charts bearing lines of magnetic variation, which did much to prevent ships from getting wrecked in foggy and stormy conditions.

The compass itself was the subject of constant innovation. Gurney steers expertly through the turgid waters of claim and counterclaim. He describes the widely used, and ineffective, compasses of the 18th-century instrument maker Gowin Knight. Knight was a persuasive showman, but his compasses were totally ineffective in rough water and condemned by the legendary navigator James Cook as "far too delicate".

Matthew Flinders charted the coasts of Australia and produced a Book of Bearings that documented compass deviation. He was ultimately responsible for the Flinders Bar, a vertical piece of iron that corrected compass deviation on binnacles.

The advent of iron-built ships further complicated the compass equation, often rendering the instrument useless, despite efforts to compensate for deviation with magnets.

Famed 19th-century hydrographer Francis Beaufort masterminded the Admiralty Compass Committee, whose studies led to Compass Number 1 with its undamped dry card. Instrument makers then competed for naval and shipping business - men such as Sir William Knight, who convinced the redoubtable Admiral "Jacky" Fisher to make his ineffective dry card compass and binnacle standard issue for the Royal Navy.

Then came compasses with liquid-mounted cards, first perfected by the US inventor E.S. Ritchie and adopted by the US Navy long before fast torpedo boats and destroyers convinced the hidebound Admiralty to adopt a similar technology. Liquid compasses gave way to gyrocompasses that pointed toward true north, surviving today only on small craft in a domed design that accommodates heeling. Few yachts, however electronically sophisticated, can afford to ship out with no compass. This ancient, failsafe navigational device can bring a sailor home when computer-based and global positioning system technologies have failed.

Compass is a well-researched excursion into an esoteric scientific world where the debates are passionate, the research often mindnumbingly dull and the commercial stakes high. Gurney's history of the subject fills a gap in maritime history, all the more authoritative because of his experience as a yacht designer.

Brian Fagan is emeritus professor of anthropology, University of California, Santa Barbara, US. He is also the author of books on sailing.