The compass came from many directions

This short history spins through many inventors' contributions

It's easy to take familiar things for granted and lose history in the process. That's happened with the magnetic compass. It has become a quaint novelty in the era of Global Positioning Satellites and inertial navigation - useful for hiking, fun to wear on a wrist-watch band to show which way city streets run. But when it acquired its modern form some eight centuries ago, it helped change the commerce and geopolitics of the Western world.

This technological wonder did not spring from an inspired inventor's eureka moment. It was the product of humanity's collective genius applied incrementally over thousands of years.

As Amir Aczel documents in this interesting little book, even Flavio Gioia of Amalfi - who reputedly made the final crucial refinements - probably didn't exist. So much for romantic notions of the hero inventor. But we can indeed marvel at the ability of human intelligence to see useful potential in natural phenomena and to realize that potential in practical ways.

We now call that ability engineering. Taken in this sense, Aczel's account of the development of the magnetic compass is an exploration into the roots of that useful profession.

The beginnings of compass development predate history. Lodestone, a naturally magnetic mineral, can magnetize iron. Mount a magnetized iron needle on wood. Float the assembly on water or suspend it on a pivot. It then will align itself with earth's magnetic field, taking up a more or less north-south direction. All relevant legends and factual accounts that have come down to us take that knowledge for granted.

The Chinese have the earliest history of the compass. Their ancestors used magnetized needles to find south - a preferred direction for divination rituals and other mystical purposes. Eventually, they appear to have used suspended needles for navigation as well.

The practice finally reached Europe. Unknown, probably Italian, inventors learned how to turn a suspended needle into a rugged navigational instrument complete with a printed card of north, south, east, west, and all intermediate directions.

Navigators who had relied on stars to find their headings now could boldly go beneath cloudy skies. Italian city-states, such as Venice, rose to power and glory, thanks to the trade advantage this gave them. European navigators eventually circled the globe with the compass's aid.

Pursuing the "riddle" of who invented the compass has been a personal quest for Aczel. Unfortunately, his hobbyist enthusiasm sometimes boils over into hype. Important as it was, the compass was not an invention that, by itself, "changed the world." Other crucial technologies - such as the spread of the Chinese invention of gun powder and general improvements in naval architecture - also drove mid-second-millennium history.

One wishes the author had given his story greater depth and set it in this broader context. Instead, we have a sketchy account fleshed out with potted histories of such relevant developments as Marco Polo's travels and the rise of Venice as a mini-superpower. If you take this essay on the level of an after-dinner conversation, it's an entertaining read. Meanwhile, we await a more incisive history.

Robert C. Cowen writes about science for the Monitor.

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